refactor background assets
finished asset constants refactoring
deleted skycontroller and skyenemy
refactoring, added gravity to player, a bug kinda fixed kinda not
Merge branch 'refactor' of github.com:wesleytsai/goodgame

Conflicts:
	goodgame.html
	js/controllers/BackgroundScroller.js
	js/controllers/SkyController.js
	js/main.js
	js/models/Enemy.js
	js/models/FishType.js
	js/models/SkyEnemy.js