added explosion effects
Merge branch 'master' of https://github.com/abbadoh/prettyGame

Conflicts:
	public/images/explosion.gif
	public/js/models/game_models/bomb_unit.js
	public/js/models/game_models/explosion_unit.js
	public/js/models/game_models/stone_unit.js
	public/js/models/gamecanvas.js
	public/js/models/gamelogic.js