Hides status bar of app
Merge pull request #1 from rafaelks/hides-statusbar

Improvement: hides app status bar
Center airplane node (not dynamic yet)
Merge pull request #2 from rafaelks/center-airplane-node

Improvement: Center airplane node (not dynamic yet)
Optimize all images
Fixed: repeat action the right way
Merge pull request #3 from rafaelks/fix-background-repeating-action

Fixed: repeat action the right way
apply world, enemi and airplane constants and physics
Merge branch 'master' into core-motion

Conflicts:
	AirWar/Controllers/Scenes/AWPlayingScene.m
using gravity to move the airplane