Animation is a first class citizen

 * Sprite constructor takes an animation instead of a string.
 * expose Animation. You can construct Animations at runtime now and assign
   them to sprites.
 * remove `chem.resources.getImage`. Use
   `chem.resources.animations[name].getImage` instead.
 * remove `sprite.setAnimationName`. Use `sprite.setAnimation` instead.
 * remove `sprite.animationName`. Use `sprite.animation` instead.
Release 3.0.0