Several fixes (Rotated AtlasRegions, Text, TextureAtlas)

Fixed: Rotated atlas regions were rotated the wrong way.
Fixed: Images reported the wrong width and height when it's source was a
rotated atlas region.
Fixed: When text removed itself from it's parent, _parent should be set
to null.
Clarified some documentation for TextureAtlas.loadTexturePacker.
Fixed:  Use of deprecated variable _world.

In Entity.get_onCamera, _world was used and should be _scene.
Fixed: Text width/height using hardware rendering.
Merge pull request #94 from MaskedPixel/dev

Several fixes (Rotated AtlasRegions, Text, TextureAtlas, Entity)