Browserify refactor

- Pixi is now completely CommonJS
- Works when compiled through browserify
- Can work in node with node-canvas with a little work
- All examples still work as before with no modifications to them
- Still generates complete compiled library, with PIXI global (building and testing is still done for it)
- Cleanup of course happened in the course of this refactor
- Removed all circular dependencies, but still needs better organization
- Some file renaming occurred to adhere to capitalized constructor module and lowercase non-constructor module