Add image assets
Get the initial asset and scene loading in place

With these changes there is now a "loading" and "main" scene. As well as
sprites being loaded for Enemy, Player, and Goal.
Merge remote-tracking branch 'origin/master'

Conflicts:
	coffee/components.coffee
	coffee/game.coffee

Currently all entities should be created in the "main" scene in game.coffee.
We will be moving away from this, but that is where they should go for now.