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.


BWAHAHAHAHA!  Thanks for the help man!