rsass 0.19.0

Early-stage sass implementation in pure rust
Documentation
# rsass

Sass reimplemented in rust with nom.
The "r" in the name might stand for the Rust programming language, for
"re-implemented", or possibly for my name Rasmus.

[![Crate](https://meritbadge.herokuapp.com/rsass)](https://crates.io/crates/rsass)
[![docs](https://docs.rs/rsass/badge.svg)](https://docs.rs/rsass)
[![Github build](https://github.com/kaj/rsass/workflows/CI/badge.svg)](https://github.com/kaj/rsass/actions)
[![Appveyor build](https://ci.appveyor.com/api/projects/status/w0hfnjwx31f7eoxj/branch/master?svg=true)](https://ci.appveyor.com/project/kaj/rsass/branch/master)

## Commandline

To make compiling faster when rsass is used as a library crate (which
is probably the dominant use-case), I have made building the
command-line utility optional.
To build the commandline, define the `commandline` feature when
building.

    cargo build --release --features=commandline

## Sass language and implementation status

The sass language [is defined in its reference
doc](http://sass-lang.com/documentation/file.SASS_REFERENCE.html).
This implementation is incomplete but getting there, if slowly.

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

If you want a working rust library for sass right now, you may
be better of with [sass-rs](https://crates.io/crates/sass-rs)
or [sass-alt](https://crates.io/crates/sass-alt),
which are rust wrappers around libsass.
Another alternative is [grass](https://crates.io/crates/grass)
which is another early stage pure rust implementation.
That said, this implementation has reached a version where I find it
usable for my personal projects, and the number of working tests are
improving.

## Contributing

Welcome! When you are reading this, chances are, you are wondering about contributing. The joyful news is that this is easy, and simple. You need not even have written any line of code.

I, the rsass maintainer, will do my best to follow both the
[Sass Community Guidelines](https://sass-lang.com/community-guidelines)
and the
[Rust Code of Conduct](https://www.rust-lang.org/policies/code-of-conduct),
and I ask you to do the same.

The first step in any contribution is probably to either try to use
the crate or to read some of the documentation.
When you do, you might find something broken, not yet implemented, or
just plain incomprehensible.
If so, please
[see if there is an issue](https://github.com/kaj/rsass/issues)
matching the problem or file a new one.

If you contribute code through a pull request, github will
automatically check that the code compiles and passes its tests with
all required versions of rust, and that the code is properly formatted
according to rustfmt.
Hopefully, I will then review the code, and either ask you for changes
or merge it.
This is a hobby project, so please excuse if the review is delayed.