Added TextureAtlas example

Includes the TextureAtlasFragment class, a new folder "assets/atlas/",
and files therein.
Cleaning up TextureAtlasFragment

Missed a few unused includes in my initial commit of the TextureAtlas
example.
Improved TextureAtlas example

Added comments and improved clarity of the TextureAtlas example
Important commit. Added my favorite beers.
Merge remote-tracking branch 'upstream/master' into scenegraph