Error with 1.0.0-alpha.4 on Windows

[AngusFu]

On Windows CMD and GitBash, it seems path seperator often cause some error.

Test the following code, where ./test.scss is any given valid scss file in the same folder:

var sass = require('dart-sass');
var res = sass.renderSync({ file: './test.scss' });
console.log(res);

Then got:

In dart.Uri_parse‘s body, insert a new line at the begining, uri = uri.replace(/\\/g, '/') will work,

So this maybe a problem to be solved.

[nex3]

This looks like it could be a bug in the glue code we use for Node.js, or possibly even in Dart itself. I may need to track down a Windows machine to test this properly.

[nschonni]

Might be a good idea to setup Appveyor for this repo to catch the Windows specific issues

[nex3]

Might be a good idea to setup Appveyor for this repo to catch the Windows specific issues

Currently our only tests are sass-spec tests of the language itself, which aren't likely to vary from OS to OS. We should probably add some tests for the CLI(s), though.