More node snapping fixes.
Merge pull request #533 from jtwigg/develop

Fix PVR's. Adjust renderScene (again).
Merge pull request #532 from slembcke/edge-snapping

More node snapping fixes.
Cocos2d submodule version updated.
Merge pull request #534 from NickyWeber/bugfix/ccbutton_alignments_update_cocos2d

Cocos2d submodule version updated.
Added Snap Anchor vs Edge Handling
Restored CCPhysicsNode as empty default
Add snap object and unify snap draw
Merge pull request #537 from cocojoe/develop

Additional snap point anchor vs edge testing
Merge branch 'develop' of https://github.com/apportable/SpriteBuilder into develop
Drag and drop of joints from plugin window onto only  other joints, NOT other nodes.