[cli] css/cssx/less/sass/stylus adapter.

So we can write styles using one or more of those languages, then do things like:

``` js
import style from 'path/to/style.less' // or path/to/style.css, path/to/style.sass, path/to/style.styl

// ...
// it's a jss stylesheet, apply it when needed:
style.attach()
```

There could be some way to handle name-spaced styles...