CSS workflow

[mstade]

This adds the css pipeline, which is essentially some basic compilation of css, including inlining @import statements – we may wish to reconsider this however as it does make actual @import statements (i.e. linked css) impossible.

This also re-implements interactive and production modes, both of which are quite naive. Production mode likely breaks source maps, however should work in debug mode. Babel source maps are flaky at this point anyway.

Subsequent work on ez-build should probably focus on linking, both of css and javascript. Javascript can possible be optimized both pre and post compilation, so future application design should probably consider implementing phase abstractions, much like a normal compiler suite would do.

[FabienDeshayes]

This is quite a large PR, I would even call it a complete rewrite. Worth a demo?

[mstade]

It more or less is, yes, but in terms of interface nearly nothing has changed (except the removal of --presets and --plugins.) It's probably not the last major overhaul either, as some of the assumptions made won't hold up when we start doing proper linking and more advanced optimizations. Defo will do a demo, once I've sorted out the node 0.12 issues.

[mstade]

Finally got the docs updated. This should be more or less ready to go once tested with another project or two.

[FabienDeshayes]

Had a quick look, it's looking neat. :+1:

[mstade]

This is done, merging.