WIP added libPVRTexTool.a
Added PNG lib to get PVR compression working. Probably going to strip it again.
remove png reader.
Merge branch 'develop' of https://github.com/apportable/SpriteBuilder into develop

Conflicts:
	SpriteBuilder/SpriteBuilder.xcodeproj/project.pbxproj
Add back in PVR Text Tool
clean memory allocs during PVR conversion.
Merge pull request #125 from jtwigg/develop

Develop