changed footstep sound, created shadowmask, replaced assets with final ones
fixed merge conflicts in Play.coffee
initialized super() in ShadowMask.coffee
Added alien sprite
Working mechanics with bullets and collisions and fun stuff.
Merge branch 'gh-pages'

Conflicts:
	library/js/min/scripts.min.js
	src/lib/Character/Enemy/Alien.coffee
	src/lib/Character/Player/Player.coffee
	src/lib/Environment/Bullet/Bullet.coffee
	src/lib/States/Play.coffee
Fixed merge conflicts with updated assets.