Adds basic rat enemy

Rat travels a horizontal path and pauses at the endpoints.  Code is bad
-- will make it pretty.
Refactors Rat enemy

Now it starts at start in both cases rather than flipping them if endX <
startX.  The pauseCounter still needs to be refactored rather than being
a global.  I might fix this.
Fixes indentation for the Rat entity
Merge remote-tracking branch 'origin/hannah'

Conflicts:
	coffee/components.coffee
	coffee/scenes.coffee