css-combine
css-combine is a module/command-line utility that combines CSS files by resolving their @import directives.

Install
$ npm install [-g] css-combine
Usage
cli
$ css-combine /path/to/file > /path/to/build
module
var combine = require('css-combine')
var raw = '/path/to/file'
combine(raw).pipe(
fs.createWriteStream('/path/to/build')
)
Note
If your @import directives use absolute file-system paths (like three.css in the above example), make sure you run css-combine from the root directory so that everything resolves correctly.
License
MIT