Changed the hit logic by adding a damage state. Damage state flashes
independent of animation now, this should be the same for all mobs.
Updated the rat look time, also updated the rat image so the look isn't
so jumpy. I'll do the clean ones later.
Merge remote-tracking branch 'origin/master'

Conflicts:
	core/src/thwack/controller/RatVsWeaponHandler.java
	core/src/thwack/model/Entity.java
	core/src/thwack/model/Player.java
	core/src/thwack/model/Rat.java
	core/src/thwack/model/Sword.java
	core/src/thwack/screen/GameScreen.java
	core/src/thwack/view/RatRenderer.java