Manually display nodes

Added a sample project that will demonstrate how to manually display nodes. Removed the UIWindow hack that coupled display of nodes with Core Animation transactions.
Merge branch 'manual-display' of github.com:facebook/AsyncDisplayKit into manual-display

Conflicts:
	examples/WaitWaitDontShowMe/Sample.xcodeproj/project.pbxproj
	examples/WaitWaitDontShowMe/Sample/AppDelegate.m
	examples/WaitWaitDontShowMe/Sample/Base.lproj/LaunchScreen.xib
	examples/WaitWaitDontShowMe/Sample/PostNode.m