Hannah

@jprof 
Adds a rat that patrols on a horizontal line.  You give it a starting position and the length of the path.  Positive sends the rat to the right, negative to the left.

Sample usage:
 @rat = Window.rat = Crafty.e 'Rat'
 @rat.attr x: 200, y: 200, w:20, h:20
 @rat.setPathLength 100
This will make the rat start patrolling at (200,200) and turn around at (300,200)


I still need to do some refactoring because the waiting mechanism is really hackish (sorry)