add extra scenes
add screen buttons and code
Merge branch 'master' into MenuScreens
add menu and play buttons
Merge pull request #15 from TinasFu/ActionAnimations

Action animations
add AppTransitionObservers and background music player
test
Merge branch 'master' into MenuScreens
deleted unused code
removed redundant self.addChild(ground) line
Merge pull request #17 from samwong000/MenuScreens

Menu screens
Sam's master
fix hero physic dynamic problem
Merge pull request #18 from samwong000/master

fix hero physic dynamic problem
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' into ActionAnimations