flexible scaling example + rebase for Cocos2D 3.1
centered backgorund image + rebase for Cocos2D 3.1
merge rebase and repo

Conflicts:
	Source/Resources/Published-iOS/Gameplay.ccbi
	Source/Resources/Published-iOS/MainScene.ccbi
	SpriteBuilder Resources/MainScene.ccb
	SpriteBuilder Resources/MainScene.ccb.ppng