Consistent tooling outputs!

So it took some real doing, but browserify/watchify/factor-bundle all should now be fully aware of the CSS dependency graph which means everything should work exactly like you'd expect. That's... not a great selling point, but an improvement over how things were!

Also the CLI now works after the changes in 0.9.x which totally broke things, I apologize!

Promises everywhere!

Wanted to support async postcss plugins like cssnano, which meant I had to rework large parts of the core to use promises for flow control. And now it's done, hooray!

API changes are visible here: https://github.com/tivac/modular-css/blob/v0.9.0/README.md#api

Nicer browserify/watchify behavior

Small release, mostly to fix #32 with #33.

Now when browserify/watchify barfs it'll look better and be way more useful!