Merge pull request #23 from Gamua/master

Fixes
context now binds the correct back buffer
controller context is now created with the 'globalContext' share group
OpenGL state cache now dependent a context

EAGLContext’s have different OpenGL state values, meaning each context
needs it’s own state cache
uniform scale no longer throws an exception if scaleX != scaleY
Merge pull request #32 from racarone/master

Context and OpenGL State Cache Fixes