fixed bug when creating a SubTexture from a render texture

Before this fix, the displayed region was wrong.
fixed Xcode analyzer warning
avoiding loops in setRotation (closes #1083)
added 'setAlpha:ofVertex:' and 'alphaOfVertex:'
converted Sparrow to ARC
converted Demo to ARC
converted Barebone to ARC
converted Scaffold to ARC
modernized Objective-C syntax
moved private members into implementation block
changed factory methods from returning concrete type to id
removed deprecated methods
renamed 'AppScaffold' project to 'Scaffold'
created 'SPViewController', incorporating functionality that was previously part of the scaffold directly into Sparrow
renamed 'SPSparrow' to simply: 'Sparrow'
changed texture classes to use 'GLKTextureLoader' internally
using new array syntax in unit tests
added support for '.gz' compressed textures
updated for Ruby 1.9
added async texture loading methods