[NOT READY] Parse v3 style natively

* [x]  Crash on exit due to unretained `uv::loop`
* [x]  Expression/filter parsing
* [x] Some tiles appear blank
* [x] Load sprite from stylesheet
* [x] Load glyphs from source object
* [x] Fix style transitions
* [x] Implement rasterization
* [ ] Fix remaining errors by porting the outdoors-gl stylesheet

This is going to break Cocoa API, which uses application of classes to perform transitions.