Add animated transparent runner
Make AnimatedSprites work

I couldn't decide if there should be both a model and a view for the
AnimatedSprite class.  I ended deciding that the state of the animation
is purely view related and so all of the functionality is within the
AnimatedSpriteRenderer.
Add an Animator class
Add and initialize an Animator
Add a width and height variable to SpriteRenderer
Make RunnerRenderer extend AnimatedSpriteRenderer
Update BitmapRenderer

Add a sourceRect and disposal of the bitmap.  The sourceRect allows the
AnimatedSpriteRenderer to use the same render function.
Update size and density of Runner