cleanup unused declarations
add new graphic assets

Using temporary asstets from the tutorial at:
http://www.photonstorm.com/phaser/tutorial-making-your-first-phaser-game
add loadSprite function
restructure modules
add physics module
change canvas size
initialize physics system
draw sky
add group module
add group type
add group function
create platforms group
add (enable/diable)Body
add create
refactor main
add world module
add worldHeight