# Changelog

All notable changes to this project will be documented in this file.

The format is based on
[Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this
project adheres to
[Semantic Versioning](https://semver.org/spec/v2.0.0.html).

## Unreleased

* Filter out placeholder selectors when writing the resulting css
  (they are still parsed of the internal data representation, so they
  can be used when implementing `@extend`) (PR #180).
* Filter out some other illegal / never-matching selectors (PR #181).
* Handle trailing comma in function arguments in plain css correctly.
* Refactored function name/plain string handling in scss values to not parse
  the same unquoted string twice.
* Remove separate backref member from `css::Selectors` for cleanup before
  implementing more selector functions.  Instead, add it to an internal
  struct `SelectorCtx` (PR #179).
* Implemented a bunch of css math functions.  They differ from the
  functions in the math module in that they fallback to themself if
  the answer cant be calculated but isn't obviously wrong
  (e.g. `min(var(--gap), 2em)` is preserved while `min(1em, 2em)` is
  evaluated to `1em` and `min(1s, 1em)` yields an error).  This also
  includes some improvements in handling numeric zeroes and
  infinities. (PR #184).
* Implemented css relative color functions (PR #185).
* Simplify units early in numeric division and multiplication.  I
  think this is a bit uglier, but it is more consistent with dart
  sass.
* Refactored some parsers for less backtracking, making it easier to point
  parse errors at the right place in the code and maybe making parsing
  slightly more efficient.
* Improve selector / name parsing by beeing more restrictive (PR #183).
* Updated sass-spec test suite to 2023-10-05.


## Release 0.28.2.

Released 2023-08-03.  This is a minor release of only rsass itself.
Progress: 4725 of 7033 tests passed

* Quoted strings can now be part of custom values (earlier, a custom value
  could be _either_ a quoted string or something else).  Thanks @kartikynwa
  for reporting (issue #175, PR #176).
* Improved handling of `calc(...)` expressions in plain css.
* Improved handling of non-interpolated `calc(...)` expressions in scss,
  they are now properly evaluated (PR #177).
* Some more (minor, mostly clippy-pedantic-suggested) internal cleanup.
* Updated sass-spec test suite to 2023-08-01.


## Release 0.28.0

Released 2023-07-09.
See also <https://rasmus.krats.se/2023/rsass028.en>
Progress: 4697 of 7032 tests passed.

* `@media` rules are now handled specifically as `@media` rules,
  rather than as unknown `@`-rules (PR #172).
* `@extend` is now explicitly unsupported (gives an error message,
  rather than behaving as an unknown `@` rule) (PR #173).
* Improved handling of `@keyframes` and `@font-face`.
* Changed output format of non-finite numbers to match sass spec.
  They are now wrapped in `calc`, like `calc(infinite)` or
  `calc(NaN * 1deg)`.
* Fixed some difference between module and builtin color functions
  `grayscale` and `invert`.
* The `deg` unit is no longer spelled out in `hsl` / `hsla` colors.
* Improved handling of custom properties in raw css input.
* MSRV of rsass (the lib crate) is now 1.60.0 (required by trancient
  dev dependency log).
* Improved parsing of quoted strings (some syntax errors was accepted).
* Removed the `Error::error(_)` shortcut for creating text-only errors
  (some text only errors remains, created directly as the
  `Error::S(String)` variant, that should probably be removed too in
  the future).
* Fixed a typo in help text, thanks @greyhillman (PR #170).
* Added an input check in selectors.append function.
* Changed `Number` internals to make values smaller in memory.
* Minor internal cleanup.
* Updated syn in rsass-macros to 2.0.2.
* Updated sass-spec test suite to 2023-06-30.


## Release 0.27.0

Released 2023-01-17.
See also <https://rasmus.krats.se/2023/rsass027.en>
Progress: 4604 of 6925 tests passed.

* Changed repo structure to a monorepo (PR #164).
  - The commandline interface now lives in the separate crate rsass-cli.
  - The test updater also have a separate crate, but not intended for
    publication.
  - Tests are restructured to fail faster for simple things, while
    macos and windows testing is added to the github action (appveyor
    is removed).
* Added macros (PR #163, #165).
  - The workspace now includes a `rsass-macros` crate that can be used to
    compile sass to css strings at compile time in rust crates.
* Changed numeric handing (mainly conversions to/from `f64`) to match
  improvements in how dart-sass handles numerics.  This is mainly done by
  removing some special cases as dart-sass and rust now agrees on more of
  those.
* Added new variables `$epsilon`, `$max-safe-integer`, `$min-safe-integer`,
  `$max-number`, and `$min-number` in `sass:math`, matching recent dart-sass
  additions.
* Added new `split()` function in `sass:string` module.
* Changed the span type used in parsing to a local type that borrows a
  `SourceFile` instead of `nom_locate` dependency (PR #158).
* Changed the type `SourceFile` to be reference counted, so cloned
  `SourceFile` objects share the same actual data (PR #158).
* Moved the `SourcePos` type into the `input` module and converted it from
  keeping a copy of the relevant line to keeping a range with a (reference
  counted) `SourceFile` (PR #158).
* Changed css creation from just writing to a text buffer to building
  a tree representation of the css (and serialize it to text as a
  final step) (PR #159).
* Changed `BinOp` value in both sass and css from a tuple variant with
  boxed values to a single boxed struct variant.
* Improved value checking; Report an error if trying to output invalid
  css values in some cases. Also, arithmetic involving colors that
  used to be calculated is now correctly invalid (PR #161).
* Changed `css::Item::AtRule` to wrap the new type `css::AtRule`.
* More varaints of `Invalid`, slightly fewer stringy errors.
* Changed handling of `hue` arguments to color functions, to allow
  different angle units, matching updates in sass-spec.
* Minor correctness improvent in the `calc` function handling.
* Clippy now takes MSRV from Cargo.toml.  Slightly more recent lints allowed.
* Updated clap to 4.0 for the command-line interface.
* Updated sass-spec test suite to 2023-01-06.

Thanks to @Wicpar for the initial macros implementation.


## Release 0.26.0

Released 2022-09-18.
See also <https://rasmus.krats.se/2022/rsass026.en>
Progress: 4500 of 6843 tests passed (or 4673 if ignoring some
deprecation messages).

### Breaking changes

* A `BuiltinFn` now takes a `&ResolvedArgs` rather than a `&ScopeRef` as
  argument (PR #157).
* `@extend` is still unsupported, but now some uses of it (e.g. in control
  structures) will result in an error instead of wrong output.
* Some `sass::Item` alternatives now contain a `Callable`, combining
  `FormalArgs` with a body (a `Vec<Item>`).  And `sass::Item::Content` now
  has a `CallArgs`.  Also, `MixinDeclImpl` is replaced with
  `sass::Closure`. (PR #146).
* `sass::CallArgs::new()` has an additional `trailing_comma` boolean
  argument (PR #147).
* Remove deprecated methods `css::Value::integer_value()` and
  `Number::is_integer()`.
* Changed the error type of `Scope::get_function()`.
* Setting a variable, `Scope::define` now takes the `Value` by value rather
  than by reference.  Also, `Scope::define_multi` is no longer exposed in
  the api.
* Renamed one variant of `ScopeError` and added two others.
* The sass `Value::Variable` and `Item::VariableDeclaration` variants
  now holds a `Name` rather than just a `String` for the variable name.
  Also, both now holds a `SourcePos`.
* Changes in `Error` representation.  Many errors are now constructed like
  `Invalid::SomeVariant.at(pos)` (PR #145).
* `Error::error` now takes an `Into<String>` argument (PR #151).
* The module `input` contains types types with `Context<L>`, `Loader`,
  `FsLoader`, and `FsContext`, replacing the old `FileContext` and
  `FsFileContext`.  Also, the types `SourceKind`, `SourceName` and `Parsed`
  are moved from top-level into the `input` module (PR #150).
* The `parse_scss_data` function is removed.  Please create a `SourceFile`
  and use the `parse` method on that instead (PR #150).
* The `Format::write_root` method are removed, `Context::transform`
  should be used instad (PR #152).

### Improvements

* `input::Context` is the new main interface to rsass.
  Create a context suitable for how files should be loaded, configure it
  with an output format and optionally extend the global scope before
  calling `Context::transform` with an input file (PR #151, PR #152).
* Also provide `CargoContext` / `CargoLoader` for convenient use in
  build scripts (PR #154).
* The way to get argument values from the implementation of a builtin
  function is refactored to handle both any type that implements
  `TryFrom<Value>` and explicit validation/conversion methods nicer, and is
  now availiable for implementing builtin functions (extensions) outside of
  rsass itself (PR #157).
* The `@content` can have arguments when declaring and calling a mixin
  (PR #146).
* Variable declartions can be scoped (like `module.$var: value`).  Some
  error reporting improvements (PR #148).
* Allow interpolation in css min and max function arguments.
* The url for `@use` and `@forward` must be quoted.
* Improve detection of import loops (PR #150).
* When loading files, Don't apply suffix / index-adding rules if the file
  name already has a suffix (PR #150).
* Some `@` rules are now forbidden in some places as they should (PR #145).
* The css `var(...)` function is now parsed as a proper function, and not
  as a special string (PR #147).
* The null value can be quoted as an empty string (PR #147).
* Make `Debug` formatting of `rsass::Error` look like the `Display` output,
  but without the "Error: " prefix. This makes the error display correctly
  if returned from a main function.  This also removed the "Error: " prefix
  from a lot of message strings (PR #151).
* In error message, don't show ellipses for consecutive lines (PR #147).
* Somtimes a trailing comma in argument lists is preserved (PR #147).
* Simplified `main` of the command-line by returning a `Result` (PR #151).
* Update sass-spec test suite to 2022-09-15.
* Handle tests referencing `input.scss` in spectest (include it among the
  mock files, if mentioned in itself or any existing mock file) (PR #150).
* Use `lazy-regex` in spectest (PR #150).
* Rsass now uses rust edition 2021, so MSRV is 1.56.0 (PR #153).
* Some cleanups.
* The main branch is now named `main` rather than `master`.

Thanks to @fasterthanlime (again) for reporting the problem with
interpolation in min and max.


## Release 0.25.2

Released 2022-05-27.
Progress: 4350 of 6552 tests passed in dart-sass compatibility mode.

* Use platform-dependent `path.join` for putting the local part after
  a base path, seems to make slash-separated strings ok as the joined
  part.  (PR #144, issue #133)
* Update sass-spec test suite to 2022-05-20.

Thanks to @fasterthanlime for reporting and testing.


## Release 0.25.0

Released 2022-05-17 (On the Norwegian Constitution day 🇳🇴).
Progress: 4331 of 6523 tests passed in dart-sass compatibility mode.

### Breaking changes

* Update minimum supported rust version to 1.49.0 (from 1.45.2).
* `SourceFile.parse()` now returns a `Result<Parsed>` rahter than a
  `Result<Vec<sass::Item>>`, and `Format::write_root` now takes a
  `Parsed` (PR #140).
* `FsFileContext::file` is replaced by `FsFileContext::for_path`,
  which initializes a file context and loads a file from it (PR 137).

### Improvements

* Hopefully improved relative file finding on windows (PR #137).
* Plain css `@import` rules is only allowed [on a few
  condtions](https://sass-lang.com/documentation/at-rules/import#plain-css-imports),
  in other cases an error is reported (Issue #139, PR #137).
* Rsass can now parse (some) plain css as well as scss.  Css files can
  be referenced in `@use` and `@import` directives, as well as in the
  `meta.load-css` mixin (PR #140).
* Make the `calc(...)` function signal an error when args are known to
  be invalid css (PR #138).
* Change `map.deep-merge` to match recent change in dart sass.
* Minor fix in whitespace around at-rules.
* Instrumented attempted file loading with `tracing` (PR #137).
* Fix a typo in LICENSE (Issue #136).
* Update sass-spec test suite to 2022-05-10.
* Make rust version of sass-spec more directory-aware (which fixes one
  of 5825 tests).
* Use a crates badge that actually works.

Thanks to @jonassmedegaard for #136, and to @fasterthanlime for
reporting the problem that #137 attempts to fix.


## Release 0.24.0

Released 2022-03-23.
Progress: 4013 of 6478 tests passed in dart-sass compatibility mode.

### Breaking changes

* The functions `parse_scss_file` and `parse_scss_path` is removed.
  Use `SourceFile` (maybe from a `FileContext`) instead (PR #132).
* Some API changes (mayinly using `SourceFile` as return type) in
  `FileContext` and `FsF ileContext` (PR #132).
* `Scope::get` now takes an `&Name` rather than an `&str` for the
  variable name.
* `sass::Value::Variable` now has a source position.
* `sass::Item` and `css::BodyItem` got new alternatives for custom
  properties (PR #134).
* Some changes in the `Error` type to facilitate positions.

### Improvements

* Basic support for `meta.load-css` mixin (PR #131).
* Improved `calc` and `clamp` handling (PR #133).
* Support custom properties (PR #134).
* Refactor source file handling.  Instead of creating new FileContexts
  wrapping the original for each file for searching for local paths in
  that file, use the SourceName of the containing file to find local
  paths (PR #132).
* Detect `@import` loops.
* Report undefined variable / module errors better.
* Update color formatting.  Sass-spec changed how it decides what
  format to show a color in (PR #135).
* Enable clippy in CI and fix some things it complained about (PR #128).
* Update sass-spec test suite to 2022-03-17.


## Release 0.23.4

Released 2022-02-06.
Progress: 3872 of 6477 tests passed in dart-sass compatibility mode.

* Different kinds of length units are now considered compatible for
  the `max` and `min` css unctions.


## Release 0.23.2

Released 2022-02-04.
Progress: 3872 of 6477 tests passed in dart-sass compatibility mode.

* Fix remaining cases of "special arguments" handling in rgb function.
* The commandline now uses clap 3.0 rather than structopt.
* Update update-tests dependency hrx-get to 0.2.0.
* Update sass-spec test suite to 2022-02-01.


## Release 0.23.0

Released 2021-12-10.
Progress: 3849 of 6444 tests passed in dart-sass compatibility mode
(this may seem like a regression, but that is caused by changes in the
test suite).

### Breaking changes

* `Error` has a new alternative, `AtError`.
* In `sass::Item`, the `Error`, `MixinCall` and `MixinDeclaration`
  variants is changed to include a `SourcePos`.  Also, a `sass::Mixin`
  contains a `SourcePos` for where it is declared.
* The fields of `SourcePos` is now private.
* The `name` of a `sass::Item::AtRule` is now a SassString.
* A `css::Value::Literal` now contains a `CssString` rather than a
  `String` and a `Quotes`.  Evaluating a `SassString` also returns a
  `CssString` (PR #118).
* The selector types are split from one `selector` module to the `css`
  and `sass` modules.  Anything that used `selector` types should now
  use either `css` or `sass` types (PR #123).

### Improvements

* A css call is just a special kind of string.
* Include position of directive or function call when reporting
  `@error` errors.
* Improve error reporting from inside mixins and functions.
* Support interpolation in `@`-rule names.
* Fixed #116: The `sass:map.merge` function was buggy.
* Fixed #119: `saturate(200%)` is allowed (the argument is not limited
  to 0..100%).
* `sass:selector` functions `append`, `nest`, and `parse` are closer
  to correct (PR #123).
* `sass:meta` functions `calc-args` and `calc-name` implemented (PR #126).
* Css strings and selectors can now be parsed directly (PR #123).
* Fixed reformatting of to-much-indented comments.
* Fixed panics in some color arithmetic (Issue #120, #121, #122, PR #125).
* Replace rand with fastrand, hopefully compile faster (PR #105).
* Unicode Private-use characters are escaped when printed.
* Updated `nom` to 7.0 and `nom-locate` to 4.0.
* Update sass-spec test suite to 2021-11-30.

Thanks to @paolobarbolini, @connorskees and @charlesxsh for reporting
issues.


## Release 0.22.2

Released 2021-07-03.
Progress: 4002 of 6180 tests passed in dart-sass compatibility mode.

* Changed the `red(..)`, `green(..)`, and `blue(..)` functions to
  always return integers. Issue #114, thanks @Keats.
* Changed the `blackness(..)` and `whiteness(..)` functions to return
  blackness/whiteness of the integer rgb approximations of the color
  rather than the exact color.


## Release 0.22.0 - 2021-06-20

Progress: 3992 of 6180 tests passed in dart-sass compatibility mode.

### Breaking changes

* The `sass::Item::MixinCall` enum alternative was modified.
* Signature changes in `css::CallArgs` and `sass:CallArgs`,
  and new alternatives in `sass::ArgsError`.
* `css::Value` has a new variant `ArgList`.
* The `OrderMap::keys()` and `values()` functions now returns iterators,
  `OrderMap::remove(key)` now returns the removed value.

### Improvements

* Better handling of mixin call bodies, the `@content` item, and the
  `content_exists` function.  Fixes #112.
* `@import` exposes things `@forward`ed in the imported module.
* Many improvements in parameter passing to functions and mixins.  PR #113.
* Some more fixes regarding function calls and modules.
* Support the `keywords` function in `sass:meta`.
* Removed some debug printouts that was accidentally left in 0.21.0.
* Update sass-spec test suite to 2021-06-14.

Thanks to @Keats for reporting #112 and #108.


## Release 0.21.0 - 2021-06-01

Progress: 3727 of 6171 tests passed in dart-sass compatibility mode.

### Breaking changes

* `value::Unit` and `value::ListSeparator` has new alternatives.
* The `List` alternative in `sass::Value` and `css::Value` is modified.
* The `Use` alternative in `sass::Item` is modified, and `Forward` added.

### Improvements

* Most of `@forward` and some more of `@use` is now supported.
  PR #109 and #110.
* Handle unknown units.  PR #101.
* List can be undecided between beeing comma-separated and beeing
  space-separated.  PR #102.
* Improved parameter handling and returned values of the supported
  selector functions.  PR #103.
* Implement `meta.module_variables` and `meta.module_functions`.
* Implement `math.div` function.
* Improved parameter checking for `hwb`, `alpha`, and `invert`
  functions in `sass:color` module.
* Support slash-separated lists. PR #111.
* The `if` function evaluates its arguments lazily.  Issue #107.
* The `--include-path` cli argument is now named `--load-path`.
* At least some documentation on all public items.
* Update sass-spec test suite to 2021-05-24.  Also include "other"
  files (for `@use` and `@import`) in rust code for the suite.

Tested with rustc 1.52.1, 1.50.0, 1.48.0, 1.45.2,
1.53.0-beta.3 (82b862164 2021-05-22), and
1.54.0-nightly (657bc0188 2021-05-31).


## Release 0.20.0 - 2021-03-25

Progress: 3456 of 5962 tests passed in dart-sass compatibility mode.

### Breaking changes

* The name of a module is no longer a `sass::Name`, but instead a `String`.

### Improvements

* A space-separated list can be a key in a map.
* The builtin modules does not inherit the global functions.
* Scope names is not `sass::Name` (`$a_b` and `$a-b` is the same
  variable, but `a_b` and `a-b` are different scopes).
* Improve `sass:map` functions `get` and `merge` and add `deep-merge`
  and `deep-remove`.

Tested with rustc 1.51.0 (2fd73fabe 2021-03-23),
1.48.0 (7eac88abb 2020-11-16),
1.46.0 (04488afe3 2020-08-24),
1.44.1 (c7087fe00 2020-06-17),
1.51.0-beta.8 (73f48e5f6 2021-03-18),
1.53.0-nightly (07e0e2ec2 2021-03-24).

### Release 0.19.2 - 2021-03-25

Version 0.20.0 was originally released as 0.19.2, but yanked as there
was a breaking change.

## Release 0.19.0 - 2021-03-14

Progress: 3371 of 5945 tests passed in dart-sass compatibility mode.

### Breaking changes

* The unit of a `Numeric` is now a `UnitSet` rather than a `Unit`.
* `Error` has new variants and a new field in `BadArguments`.
* A sass::Value::Call now has a source position.
* A `Rational` is now a `Ratio<i64>` rather than a `Ratio<isize>`.

### Improvements

* Added a Contributing section to readme.
* Handle values with multiple units. PR #97.
* Show call position for errors in function calls, and test for type
  errors in many standard functions. Many error messages are made
  identical to dart-sass, improving test-suit progress with more than
  400 tests.  PR #99.
* Fix issue #98: overflow in rational number arithmetic.
* Allow `@at-root` at document root.
* Boolean operators is truly lazy, e.g. `false and f($x)` does not call `f`.
* Refactored number parsing to use overflowing rationals. PR #100.
* Test suite sass-spec updated to 2021-03-02.
* Updated num-rational and num-bigint to 0.4.0.

Thanks to @alvra for reporting #98.

Tested with rustc 1.50.0 (cb75ad5db 2021-02-10),
rustc 1.48.0 (7eac88abb 2020-11-16),
rustc 1.46.0 (04488afe3 2020-08-24),
rustc 1.44.1 (c7087fe00 2020-06-17),
rustc 1.51.0-beta.6 (6a1835ad7 2021-03-12), and
rustc 1.52.0-nightly (acca81892 2021-03-13).


## Release 0.18.0 - 2021-02-25

Progress: 2892 of 5945 tests passed in dart-sass compatibility mode.

### Breaking changes

Lots of things have been moved around.  See `Scope`, `Numeric`, and
`Function` in particular.

### Improvements

* Support `@use` of user-defined modules.  PR #96.
* Improve trigonometric precision by using f64 π rather than rational.
* Handle more peculiarities with atan2, pow, infinities and negative zero.
* Improve name lookups in scopes and modules, PR #87.
* new `struct Scope` replaces trait and three structs. PR #95.
* A color can be Hsla or Hwba as well as Rgba. PR #88, #89.
* Handle units in `@for` loops inside sass functions.
* Some types moved into `value` mod, imporoved docs. PR #90.
* Add support for `$=`, `~=` and `^=` in css attribute selectors.
  Issue #91, PR #92.
* A `Numeric` is a Number with a Unit.  Also hide NumValue enum. PR #93.
* The `SassFunction` type is now named `sass::Function`.
* Test suite sass-spec updated to 2021-02-18.
* Some cleanups.

Thanks to @mfeckie for #91/#92.

Tested with rustc 1.50.0 (cb75ad5db 2021-02-10),
rustc 1.48.0 (7eac88abb 2020-11-16),
rustc 1.46.0 (04488afe3 2020-08-24),
rustc 1.44.1 (c7087fe00 2020-06-17),
rustc 1.51.0-beta.3 (b631c914c 2021-02-24), and
rustc 1.52.0-nightly (a8486b64b 2021-02-24).

## Release 0.17.0 - 2021-01-29

Progress: 2784 of 5936 tests passed in dart-sass compatibility mode.

### Breaking changes

* Update nom to 6.0 raises the minimally supported compiler version
  to 1.44.0.  Also, the dependency is technically exposed.
* `sass::Item::Use` was modified by #84.
* `compile_scss_file` is renamed to `compile_scss_path`, and
  `FileContext` is now a trait, the default implementation is renamed
  to `FsFileContext` by #85.

### Improvements

* Allow customizing file loading by providing a custom impl of a
  `FileContext`, PR #85.
* Support the `@use name as *` syntax, PR #84.
* Make `Error::BadValue` a little closer to whats expected.
* Handle units in `@for` loops.
* Update `nom` to 6.0, PR #83.
* Update `rand` to 0.8, PR #86.
* Testing is now done with github actions rather than travis
  (Appveyor remains for window builds).
* sass-spec test suite updated to 2021-01-20.

Thanks to @paolobarbolini and @alvra for code contributions.

Tested with rustc 1.49.0 (e1884a8e3 2020-12-29),
1.44.1 (c7087fe00 2020-06-17), 1.46.0 (04488afe3 2020-08-24),
1.48.0 (7eac88abb 2020-11-16), 1.50.0-beta.8 (1cd030396 2021-01-20),
and 1.51.0-nightly (c0b64d97b 2021-01-28).

## Release 0.16.0 - 2020-11-10

Progress: 2718 of 5840 tests passed in dart-sass compatibility mode.

### Breaking changes

* `SourceName` and `sass::Item::Import` was changed by #62.
* `Use` was added to the `sass::Item` enum by #80.
* Changes to `sass::Value` and `css::Vaue` by #81.

### Improvements

* PR #80: Implement `@use` for standard sass modules.  All standard
  modules are at least partially supported, only `sass:string` is
  fully supported.  See issue #60 for for module support status.
* PR 82: Implement hwb support in `sass:color`.
  Also, provide `From<Rgba>` for `css::Value` and deprecate color
  value constructors.
* Provide `From<bool>` for `css::Value` (and deprecate `Value::bool(v)`).
* PR #62: Improve `ParseError`, `SourcePos`, and `SourceName` by using
  located spans by [nom_locate](https://lib.rs/crates/nom_locate) in
  the parser.  A `sass::Item::Import` now handles where each file is
  imported from, to improve error reporting.
* PR #81: Improved number handling.  Now `Value::Number` handles both
  machine-sized rationals, bignum rationals and floats internally and
  `Value::NumberBig` is removed.  Also, `Value` no longer implements
  `Ord` but only `PartialOrd`, to handle f64 NaN an infinite values
  correctly.
* Improve parsing of `@else` clauses.
* Update spec to 2020-10-29.

Tested with rustc 1.47.0 (18bf6b4f0 2020-10-07),
1.44.1 (c7087fe00 2020-06-17), 1.42.0 (b8cedc004 2020-03-09),
1.40.0 (73528e339 2019-12-16), 1.38.0 (625451e37 2019-09-23),
1.48.0-beta.8 (121901459 2020-11-08), and
1.49.0-nightly (25f6938da 2020-11-09),


## Release 0.15.0 - 2020-10-25

Progress: 2320 of 5577 tests passed in dart-sass compatibility mode.

### Breaking changes

* The `Item::Comment` enum value now contains a `SassString` rather
  than a `String`.
* The `Error::ParseError` enum value changed, and `ErrPos` is replaced
  with `SourcePos` and `SourceName`.
* The error type of `parse_scss_data` changed to `ParseError`.
* `Unit::dimension()` now returns a `Dimension` rather than a `&str`.

### Improvements

* PR #79: Refactor some error handling.  Relates to #46.
* Improve map parsing (a map is parsed as a plain vec of key/value
  pairs, filtering duplicates happens only when it is evaluated).
* Allow multiple `&` items in the same selector.
* `&` evaluates to null when used as a value without enclosing selector.
* Implement the `@debug` directive.
* Fix `a % b` evaluation for negative values.
* Allow / ignore comments in properties and values.
* Allow `!default` and `!global` in any order on variable declarations.
* Improve `inspect(...)` formatting of list values.
* Refactor and improve arithmetic on different units.
* `ListSeparator` is now `Copy`.
* Allow interpolation in comments.
* Some refactoring

Tested with rustc 1.47.0 (18bf6b4f0 2020-10-07),
1.44.1 (c7087fe00 2020-06-17), 1.42.0 (b8cedc004 2020-03-09),
1.40.0 (73528e339 2019-12-16), 1.38.0 (625451e37 2019-09-23),
1.48.0-beta.5 (4c78178b1 2020-10-21), and
1.49.0-nightly (ffa2e7ae8 2020-10-24).

## Release 0.14.2 - 2020-10-13

Progress: 2294 of 5577 tests passed in dart-sass compatibility mode.

* Some improvements in list handling, formatting and introspection.
* Change default precision to 10, matching dart-sass.
* Semicolon is optional after variable, if last in block or file.
* Fix addition (and subtraction) of values with comparable units.
* Fix css value equality for map keys and other "special" places.
* Recognize known `@`-rules with escaped characters.
* Don't copy extra `@charset` rules to output (one is included if
  needed).
* Some internal refactor and cleanup.
* Update spec to 2020-10-07.

Tested with rustc 1.47.0 (18bf6b4f0 2020-10-07),
1.44.1 (c7087fe00 2020-06-17), 1.42.0 (b8cedc004 2020-03-09),
1.40.0 (73528e339 2019-12-16), 1.38.0 (625451e37 2019-09-23),
1.48.0-beta.2 (212e76c31 2020-10-08), and
1.49.0-nightly (8dae8cdcc 2020-10-12)


## Release 0.14.0 - 2020-10-03

Progress: 2234 of 5510 tests passed in dart-sass compatibility mode.

* PR #76 and #78: Target dart-sass rather than libsass compatibility.
  This sets the target when testing and changes some different
  behavior, including how strings are parsed and handled.
* PR #75 from @divergentdave: Parse and add `Value` variants for
  BigInt numbers
* PR #77: Support `rgba(r g b / a)` and `hsla(h s l / a)` functions,
  i.e. the `channels` parameter with div-separated alpha channel.
* Fix `@import` indention.
* Improve function default argument parsing and don't panic in
  `parse_value_data`.
* Handle dictionary-ellipsis style call-by-varargs for functions.
* PR #73 from @divergentdave: Remove three unwraps from escaped_char
* PR #71 from @connorskees: Further optimize number printing
* Update travis url in README.
* PR #70 from @svenstaro: Mention grass rather than sassers, as
  sassers appears to be dead while grass is in rather active
  development.
* Add a CHANGELOG.md
* Update spec to 2020-09-17.
* Update num-rational to 0.3.0.

Tested with rustc 1.46.0 (04488afe3 2020-08-24),
1.44.1 (c7087fe00 2020-06-17), 1.42.0 (b8cedc004 2020-03-09),
1.40.0 (73528e339 2019-12-16), 1.38.0 (625451e37 2019-09-23),
1.47.0-beta.7 (e28d2bd09 2020-10-01), and
1.48.0-nightly (8876ffc92 2020-10-02)


## Release 0.13.0 - 2020-04-19

Progress: 1634 of 3502 tests passed in libsass compatibility mode.

* output::Format wraps an output::Style and a precision.  The global
  precision setting is removed.
* Value and other structs no longer implents Display, instead the
  provid a `format` method, that takes an output format and provides a
  Display implementation.
* The `compile_value` rust function now takes a format argument.
* Issue #42 (partial): The `min(..)` and `max(...)` functions are
  handled as plain css functions when valid, while still handling them
  as sass functions when nessecary.
* PR #69, fixing #68: Avoid exponential complexity on parenthesis.
* Allow comments in `@function` bodies.
* PR #67 from @connorskees: Refactor and fix printing of numbers
* When defining multiple variables, having more names than values is
  allowed.  The extra names get null values.
* Convert som panics / unwraps to properly handled errors.
* There was massive restructuring in the test suite, so almost all
  tests moved around.  I moved remaining tests to build a single test
  program for the suite rather than several for different directories
  in the suite (this also means more tests are included in the
  conversion).
* Fix check_spec stats calculation.

Thanks to @connorskees for code contributions and bug reports.

Tested with rustc 1.42.0 (b8cedc004 2020-03-09),
1.40.0 (73528e339 2019-12-16), 1.38.0 (625451e37 2019-09-23),
1.36.0 (a53f9df32 2019-07-03), 1.43.0-beta.6 (062dea094 2020-04-18),
and 1.44.0-nightly (52fa23add 2020-04-18).


## Release 0.12.2 - 2020-02-23

* Fix #63 and #64: Handle DOS-style newlines
* Use structopt rather than raw clap for the CLI.
* Sass function `str_slice` require integer indexes.
* Some cleanup, some of it suggested by clippy.
* Removed link to no-longer working graphical progress bar in docs.

Thanks to @connorskees for bug reports.

Tested with rustc 1.41.0 (5e1a79984 2020-01-27),
1.40.0 (73528e339 2019-12-16), 1.38.0 (625451e37 2019-09-23),
1.36.0 (a53f9df32 2019-07-03), 1.42.0-beta.3 (86f329b41 2020-02-07),
and 1.43.0-nightly (436494b8f 2020-02-22).


## Release 0.12.0 - 2019-12-25

* Issue #54: Add a LICENSE file.
* PR #57: Allow channel string in rgba()
* Issue #58: Let ructe::Error implement std::error::Error.
* Issue #59: Improve `@import` and media rules.
* Implement `@error` and `@warn` directives.
* Improve string unquoting, including multi-position numerical
  escapes.
* Improve at-rule parsing.
* Fix strange operator handling.
* Implement modulo operator.
* Fix line breaks in comments.
* Handle bad argument to `random()` function.
* Update test suite to e9e219bdf (2019-12-19).
* Some refactorig and clean-up.

Thanks to @emielbeinema, @maxbrunsfeld, and @Boiethios for contributed
code and suggestios.

Tested with rustc 1.40.0 (73528e339 2019-12-16),
1.38.0 (625451e37 2019-09-23), 1.36.0 (a53f9df32 2019-07-03),
1.34.2 (6c2484dc3 2019-05-13), 1.41.0-beta.1 (eb3f7c2d3 2019-12-17),
and 1.42.0-nightly (a9c1c04e9 2019-12-24).


## Release 0.11.2 - 2019-12-25

* PR #56:  The url function is special.
  Handle `url(foo)` as simply a string if possible.  Sometimes, such
  as `url("foo" + $bar)`, it must be a function returning a string
  instead.  Partially adresses #42.  Fixes #41.
* PR #55: Implement raw css functions.
  Handles the `calc`, `element`, `env`, `expression`, `var`, and
  `progid:...` special functions.  Partially adresses #42.  Fixes #53.
* Issue #50: Make tests more readable.
* Improve error handling in selector fns.
  Avoid a panic in some error conditions.
* Update test suite (to fcd6bd6c0, 2019-09-24).
* Update bytecount to 0.6.0.
* Some internal refactoring.

Thanks to @glebm and @nic-harley for reports and suggestions.


## Release 0.11.0 - 2019-07-16

Sass-spec reports 1507 of 2865 tests passed in libsass compatibility
mode.

* Update `nom` to version 5.0.
* A string can start with a `#` without being a color.
* Correct parameter name for `unit`, `unitless`, `quote`, and
  `unquote` functions.
* The `random` function ignores units.
* An empty unquoted string behaves like null.
* Fix some issues with string offsets in `str_slice` and `str_insert`.
* The `quote` function can use single quotes when needed.
* Return an error rather than panicing on some invalid scss.
* Some test updates and fixes in spectest.

Tested with rustc 1.36.0 (a53f9df32 2019-07-03),
1.34.2 (6c2484dc3 2019-05-13), 1.32.0 (9fda7c223 2019-01-16),
1.37.0-beta.3 (2ba6de7e2 2019-07-12), and
1.38.0-nightly (4b65a86eb 2019-07-15).



## Release 0.10.2 - 2019-07-07

Sass-spec reports 1472 of 2802 tests passed in libsass compatibility mode.

* Update progress number in readme and documentation, since I forgot
  in 0.10.0.


## Release 0.10.0 - 2019-07-07

* PR #51: Impove string parsing/escaping.
* Issue #46, PR #47: Report file position of parse errors, and improve
  the parser to have errors reported in a more specific position.
* Improve error handling in functions, calling a function _can_ yield
  an error.  Partially solves #41: The unsupported call will now yield
  an error rather than hang `rsass`.
* Commandline changes:
  - Support `-I` commandline argument for include path.
  - Use lowercase `-v` for version (expected by the test runner).
* Some color function improvements:
  - Handle alpha percentatges in rgba.
  - The rgb function can be used as rgba with four args.
  - Use alpha propely when mixing colors.
  - Handle both alpha and opacity css function fallback.
  - Implement the grayscale function.
  - Support three arguments to `rgba` function.
* Some list function improvements:
  - `inspect` shows parens for empty list, and spells out `"null"` for
    a null value.
  - Join gets better at selecting wether result should be comma or
    space separated.
  - The length function treats a null as an empty list.
  - Handle singleton in `index` and `nth` functions.
* More function improvements:
  - Implement the `unique_id` function.
  - Check that indexes are sane in `str_slice` function.
  - Skip null args even if not last when evaluating a function to a
    function call.
  - Implement equality check for builtin functions.
* Error, not panic, on unknown mixin.
* Allow modifiers on attribute selectors.
* Color names are caseless.
* Improve handling of url imports.
* Update `deunicode` to 1.0 and `rand` to 0.7.0.
* Allow interpolation in namespacerule.
* Allow ";" after body block.
* Lots of test suite updates, including support for .hrx tests in
  spectest.  Target libsass compatibility in testing.

I don't really know if I should target libsass or dart-sass
compatibility, but libsass seems to be closer to my current
implementation, so target that at least for now.

Thanks to @maxbrunsfeld and @glebm for code and suggestions.

Tested with rustc 1.36.0 (a53f9df32 2019-07-03), 1.34.2 (6c2484dc3 2019-05-13), 1.32.0 (9fda7c223 2019-01-16), 1.37.0-beta.1 (178aa6611 2019-07-04), and 1.38.0-nightly (481068a70 2019-07-05).


## Release 0.9.8 - 2019-02-10

Sass-spec reports 1645 of 3440 tests for sass 3.6 passed.

* Improve support for `transparent`.
* PR #45 from @glebm: Automatically update passing / failing tests
  Hardkoded skiplists in spectest.rs is cleared apart for tests where
  rsass panics.
* Issue 43: Normalize newlines in tests.
* PR #44 from @glebm: Update to Rust 2018 Edition, Rust v1.31.0+
* Issue #39, PR #40 from @glebm: Parser CallArgs: Allow trailing
  spacelike sans ","
* Issue #32: Make the selectors module pub.
* Issue #34, PR #35 from @glebm: Accessing an undefined variable is an error.
* Allow input starting with UTF-8 U+FEFF BOM.
* Target sass spec version 3.6.

Thanks to contributors @glebm, @maxbrunsfeld and @sunjay for code and
suggestions.

Tested with rustc 1.32.0 (9fda7c223 2019-01-16),
1.31.0 (abe02cefd 2018-12-04), 1.33.0-beta.6 (b203178b6 2019-02-05),
and 1.34.0-nightly (3315728c0 2019-02-09).


## Release 0.9.6 - 2019-01-09

A default run of sass-spec found 1680 of 3635 tests passing.

* Issues #26, #30, PR #29 from @tw1t611; Add `fr` unit.
* Refactor and document the Number type used inside value types.
* Allow trailing comma in sass function definitions.
* The sass `length` function now correctly returns one for single
  (non-list) values.
* Fix a bug in color function parameter handling.
* Add libsass and parser to auto-testing setup.
* Update rand to 0.6.1.

Tested with 1.31.1 (b6c32da9b 2018-12-18),
1.30.1 (1433507eb 2018-11-07), 1.29.0 (aa3ca1994 2018-09-11),
1.28.0 (9634041f0 2018-07-30), 1.27.2 (58cc626de 2018-07-18),
1.26.2 (594fb253c 2018-06-01), 1.32.0-beta.12 (2bde39b8e 2019-01-05),
and 1.33.0-nightly (d22fa2d87 2019-01-08)


## Release 0.9.4 - 2018-09-23

A default run of sass-spec found 1672 of 3483 tests passing.

* Allow unicode variable names.
* Implement the precision argument.
* Implement hex colors with alpha.
* More flexible call_args; allow whitespace before separating commas,
  and allow a comma trailing the last argument.
* Test infrastructure: a program spectest now converts selected tests from
  sass-spec to integration tests, to facilitate keeping tests up-to-date.

Tested with rust 1.29.0 (aa3ca1994 2018-09-11),
1.28.0 (9634041f0 2018-07-30), 1.27.2 (58cc626de 2018-07-18),
1.26.2 (594fb253c 2018-06-01), 1.25.0 (84203cac6 2018-03-25),
1.30.0-beta.7 (0ebb25088 2018-09-22), and
1.30.0-nightly (4591a245c 2018-09-22).


## Release 0.9.2 - 2018-09-02

* Fix #25; Avoid crashing on some non-utf8 input.

Thanks again to @killercup and rust-fuzz/targets#119 for identifying
more parser crashes on non-utf8 input.

Tested with rustc 1.28.0 (9634041f0 2018-07-30),
1.27.2 (58cc626de 2018-07-18), 1.26.2 (594fb253c 2018-06-01),
1.25.0 (84203cac6 2018-03-25), 1.24.1 (d3ae9a9e0 2018-02-27),
1.29.0-beta.9 (b4ec8d46e 2018-09-01), and
1.30.0-nightly (28bcffead 2018-09-01).


## Release 0.9.0 - 2018-08-26

A default run of sass-spec found 1661 of 3482 tests passing.

Changes since version 0.8.0 includes:

* PR #24: Implement a Rgba type and use in css::Value and sass::Value.
* PR #22: Partial support for `@at-root`.  Supports `&` back-refs but
  not `with` and `without`.
* Add "foo/index.scss" and "foo/_index.scss" when attempting to find
  "foo" for import.
* The parser should fail rather than crash on some non-utf8 input.
* PR #21: Introduce a Number type, mainly for sharing some abstraction
  between css and sass values.
* Make the `rgba` function handle non-numeric inputs (e.g. calc(...)).
* Implement the `feature-exists` function.
* Make `!important` part of value rather than property, so it can be
  used in function / mixin arguments etc.
* A css3 pseudo-element selector may have arguments.
* Add support for unicode ranges.
* The `@each` construct can bind multipe values.
* PR #20: Division is now a BinOp rather than a special case.
* Minor improvement in parsing and formatting at-rules.
* Fix some clippy complaints.
* Minor documentation updates.
* Some updates to travis build script and test structure.
* Add appveyor (windows) continous integration testing.
* Depedency updates: num-rational 0.2.1, nom 4.0 (PR #23) and rand 0.5.

Thanks to @killercup and rust-fuzz/targets#119 for identifying some
parser crashes on non-utf8 input.

Tested with rustc 1.28.0 (9634041f0 2018-07-30),
1.27.2 (58cc626de 2018-07-18), 1.26.2 (594fb253c 2018-06-01),
1.25.0 (84203cac6 2018-03-25), 1.24.1 (d3ae9a9e0 2018-02-27),
1.29.0-beta.6 (5c5be098e 2018-08-25), and
1.30.0-nightly (39e6ba821 2018-08-25).


## Release 0.8.0 - 2018-04-07

A default run of sass-spec found 1583 of 3364 tests passing.

Changes since version 0.7.0 includes:

* PR #17, #18, and #19 from @ErichDonGubler: Improvements to `check_spec`.
* Allow trailing comma in dictionary definition.
* Implement the `get-function` function, making a (named) function a
  css::Value, and modify the call function to take such a Value.  The
  warning when the Value is a Literal is more motivated now.
* Add weight arg for invert function.
* If a function call fails, output it as-is.
* Allow `@include` w/o ";" to be last input.
* Use correct names for output styles.  The supported styles are
  `expanded` and `compressed`.
* Add maintenence status to manifest.
* Impement the `&` value, expanding to the selector containing the
  value.
* Implement the `selector-parse`, `selector-append`, and
  `selector-nest` functions.
* Fix AsciiExt warning on rust 1.23 and up.
* Fix #16, Do not build a no-op command line, by specifying commandline as
  required-features of the bin target.
  Thanks to @biluohc for the suggestion!
* Miscellaneous code cleanup, dependency updates and reformatting.

Tested with rustc 1.23.0 (766bd11c8 2018-01-01),
1.24.1 (d3ae9a9e0 2018-02-27), 1.25.0 (84203cac6 2018-03-25),
1.26.0-beta.2 (0e350672e 2018-04-05), and
1.27.0-nightly (eeea94c11 2018-04-06).


## Release 0.7.0 - 2017-12-28

A default run of sass-spec found 1466 of 3339 tests passing (or 1520
of 6094 when claiming to be libsass). Changes since version 0.6.0
includes:

* Fix #15 by making building the commandline utility optional.
* Fix some issues with string quoting and list whitespace.
* Improve support for `@`-rules.
* Use num-rational without default features, for faster compilation.

Tested with rustc 1.19.0 (0ade33941 2017-07-17),
1.20.0 (f3d6973f4 2017-08-27), 1.21.0 (3b72af97e 2017-10-09),
1.22.1 (05e2e1c41 2017-11-22), 1.23.0-beta.2 (c9107ee93 2017-12-08),
and 1.24.0-nightly (1abeb436d 2017-12-27).


## Release 0.6.0 - 2017-12-06

A default run of sass-spec found 1466 of 3339 tests passing (or 1520
of 6094 when claiming to be libsass). Changes since version 0.5.0
includes:

* Handle quoting and escaping in strings closer to correct.
* Updated lazy_static to version 1.0
* Some internal cleanup.

Tested with rustc 1.19.0 (0ade33941 2017-07-17),
1.20.0 (f3d6973f4 2017-08-27), 1.21.0 (3b72af97e 2017-10-09),
1.22.1 (05e2e1c41 2017-11-22), 1.23.0-beta.1 (082b0ff02 2017-11-21),
and 1.24.0-nightly (cfba0d446 2017-12-05).


## Release 0.5.0 - 2017-11-05

A default run of sass-spec found 1359 of 3331 tests passing (or 1416
of 6086 when claiming to be libsass). Changes since version 0.4.0
includes:

* Improve handling of quoted / unquoted strings and interpolation.
  Still not correct, but exhibits correct behavior in more tests than
  earlier.
* Support interpolation in selectors.
* Support interpolation in property names.
* PR #14: Implement map syntax and map functions.
* Make error handling not break if nom is compiled with verbose-errors.
* Miscellaneous internal cleanups, some suggested by clippy.

Tested with rustc 1.18.0 (03fc9d622 2017-06-06), 1.19.0 (0ade33941
2017-07-17), 1.20.0 (f3d6973f4 2017-08-27), 1.21.0 (3b72af97e
2017-10-09), 1.22.0-beta.2 (a0a837c45 2017-10-20), and 1.23.0-nightly
(d762b1d6c 2017-11-04).


## Release 0.4.0 - 2017-10-15

A default run of sass-spec found 1163 of 3331 tests passing (or 1227
of 6086 when claiming to be libsass). Changes since version 0.3.4
includes:

* Implemented bracketed lists.
* Support CSS3 pseudo elements
* Added functions: `unitless`, `content-exists`, `zip`,
  `is-bracketed`, `join`.
* Update the nom parser library to 3.2.
* PR #13 Split of css values from sass values.
* PR #10 Preparatory work for splitting Value
* PR #7 Extract parser into separate module
* PR #8 Extract som modules from lib.rs
* Pin rustfmt to 0.8.4, to avoid surprising formatting changes.
* PR #6 Don't require a git plugin for the check-spec.

Thank You to [Jonas Nicklas](https://github.com/jnicklas) for many
contributions.

Tested with rustc 1.18.0 (03fc9d622 2017-06-06), 1.19.0 (0ade33941
2017-07-17), 1.20.0 (f3d6973f4 2017-08-27), rustc 1.21.0 (3b72af97e
2017-10-09), 1.22.0-beta.1 (e694dd37b 2017-10-12), and 1.22.0-nightly
(7778906be 2017-10-14).


## Release 0.3.4 - 2017-06-05

A default run of sass-spec found 1146 of 3310 tests passing (or 1215
of 6065 when claiming to be libsass). Changes since version 0.3.2
includes:

* Improve handling of at-rules.
* Allow block comments in selectors.
* Make FileContext::file(..) public.
* Test and fix type-of for booleans.
* Test and fix parsing of some strange lists.
* Test and fix unary operations.
* Test and fix some strange string values.
* Some internal cleanup and code restructuring.

Tested in rust 1.15.1 (021bd294c 2017-02-08), 1.16.0 (30cf806ef
2017-03-10), 1.17.0 (56124baa9 2017-04-24), 1.18.0-beta.4 (0308c9865
2017-05-27), and 1.19.0-nightly (0418fa9d3 2017-06-04).


## Release 0.3.2 - 2017-05-06

A default run of sass-spec found 1053 of 3299 tests passing (or 1111
of 6054 when claiming to be libsass). Changes since version 0.3.0
includes:

* Clean up nom error creation, to be compatible with both default and
  verbose-errors nom.
* Implement some more quote strangenes.
* Minor internal cleanup

Tested in rust 1.15.1, 1.16.0, 1.17.0 (stable), 1.18.0-beta.1
(4dce67253 2017-04-25), and 1.19.0-nightly (f4209651e 2017-05-05).


## Release 0.3.0 - 2017-05-06

A default run of sass-spec found 1039 of 3299 tests passing (or 1097
of 6054 when claiming to be libsass). Changes since version 0.2.0
includes:

* PR #4: Support application-defined functions in rust.
* Equal strings are equal even if the quoting differs
  (e.g. foo == "foo").
* Improved value parsing in many ways.
* Implemened numeric rounding rules to match libsass default.
* Improved handling of null values.
* Fix some minor output formatting issues.
* Handle arguments to pseudo-selectors (which are themselfs selectors)
  properly.
* Support for rust 1.14 is dropped.

Tested in rust 1.15.1, 1.16.0, 1.17.0 (stable), 1.18.0-beta.1
(4dce67253 2017-04-25), and 1.19.0-nightly (f4209651e 2017-05-05).


## Release 0.2.0 - 2017-04-28

A default run of sass-spec found 841 of 3294 tests passing (or 899 of
6049 when claiming to be libsass). Changes since version 0.1.10
includes:

* Err results from public functions is now `Error`, not `String`.
  This is a breaking change in public api.
* PR #2: value interpolation (as separate values and in strings).
* Implement basic `@content` for mixins (some scoping issues remains).
* Support namespace properties.
* Improve parsing of unquoted strings.
* Implement the `call()` function.
* Implement the `ie-hex-str()` function.
* Allow alternative parameter names to `rgba()` function.
* Improve defered operators handling.
* Improve scopeing and value evaluating (but not enough).
* Allow function declarations in blocks.
* Implement `for`, `while`, and `each` in user-defined functions.
* Fix scoping error for while loops.
* Support css unary + and -.
* Misc internal or smaller improvements (some suggested by clippy).

Tested in rust 1.14.0, 1.15.1, 1.16.0, 1.17.0 (stable), 1.18.0-beta.1
(4dce67253 2017-04-25) and 1.18.0-nightly (94e884b63 2017-04-27).


## Release 0.1.10 - 2017-04-14

* Improve string concatenation with plus operator.
* Support `*` in selectors
* Support `\` in selectors
* Support varargs functions.
* Allow trailing commas in lists.
* Implement list functions `append`, `length`, and `index`.
* Implement numeric functions `min` and `max`.
* Improve `@for` and `@each` loop handling.
* Internal cleanup and refactorisation.

Tested in rust 1.14.0, 1.15.1, 1.16.0 (stable), 1.17.0-beta.3 (beta),
and 1.18.0-nightly (28a742997 2017-04-13).


## Release 0.1.8 - 2017-04-08

A default run of sass-spec found 576 of 3294 tests passing (or 619 of
6049 when claiming to be libsass). Changes since version 0.1.6
includes:

* Support user-defined functions.
* Support functions `global_variable_exists`, `function_exists`,
  `mixin_exists`.
* Support `@each`, `@for` and `@while` loops.
* Make dash and underscore equivalent in names.
* Fix all tests from `spec/scope`.
* Improve documentation.
* Miscellaneous refactorisations and cleanups.

Tested in rust 1.14.0, 1.15.1, 1.16.0 (stable), 1.17.0-beta.3 (beta),
and 1.18.0-nightly (53f4bc311 2017-04-07).


## Release 0.1.6 - 2017-03-05

A default run of sass-spec found 502 of 3289 tests passing (or 532 of
6044 when claiming to be libsass). Changes since version 0.1.4
includes:

* Many more functions implemented.
* Better support för `at` directieves.
* Support the `!default` tag on variable declaration.
* Support all known css units.
* Support `!important` tag on properties.
* Allow the `*` character inside comments.

Tested in rust 1.14.0, 1.15.1, 1.16.0-beta.3 (stable), and
1.17.0-nightly (b1e31766d 2017-03-03).


## Release 0.1.4 - 2017-02-08

A default run of sass-spec found 420 of 3286 tests running (or 449 of
6041 when claiming to be libsass).

* Very basic support for media queries.
* Implement more color functions (the internal representation of a
  color now uses Rational for the channels, to avoid rounding errors
  when using the result of one color function as input to another).
* More complete parsing of simple numbers.
* Support ambiguous imports, as examplified by basic test 33.
* Use the `?` operator rather than the `try!` macro.
* Proper handling of escaped quotes in quoted strings (basic test 53).
* Miscellaneous internal cleanups and refactorings

Tested in rust 1.14, 1.15, and stable and nightly as of 2017-02-08.


## Release 0.1.2 - 2017-01-29

Second release. Passes 380 tests of 6026 from sass-spec. Changes since 0.1.0 include:

* Basic pseudo-classes.
* Functions return a Result (so they can fail without panic). Note
  that all other error handling is still simply panics.
* Implemented functions `str-slice`, `str-insert`, `str-length`.
* Documentation


## Release 0.1.0 - 2017-01-22

First release to crates.io.  Passes 346 tests of the sass-spec suite.


## Initial commit - 2016-12-20

The first three tests (of several thousand) works.  :-)
