Allow a Skeleton instance to be created without supplying SkeletonData at the time of construction.
Allow a dynamic Object to be passed to readSkeletonData.  Currently allows json text string as a String or a ByteArray.  Now allows you to supply an Object that's already been parsed.
Make the _skeleton member variable protected instead of private so that classes that might extend SkeletonSprite have write access to it.
Fix implementation of additiveBlending.  Now correctly restores the blendMode by storing the original blend mode from RenderSupport at the top of the function.  Since the instance's blendMode is often set to AUTO, it can't be used to restore the blendMode.  AUTO will not actually change the internal mBlendMode variable in the RenderSupport instance, and the blendMode will remain ADD if it was ever set to it once.