Refactored main a bit. Bumped version to 0.0.4.
Merge branch 'release/0.0.4'

Behind the scenes minor release. Change log:
* Optimized level loading for 6-10x speed up.
* Smaller atlases (non-square support).
* Refactored and simplified shaders.
* Refactored level building to a more generic system.
Merge tag '0.0.4' into develop