Attach an attack movieClip to a sprite
- set attacks via its "type" array
It checks for collision with other enemies' "hit" boxes,
then calls their reaction methods based on the attack's "type"
"stomp" attack calls enemy's  react.stomp()  reaction.
The attack skips it's parent sprite.

Attack types
- none
- misc
- stomp
- projectile
- spike
- instantDeath

Enemy reaction functions may detect direction of attack
(the attacker is passed to the function)
which is helpful for stomp reactions, and collision physics.



Each sprite stores its state in a "state" variable
which allows for conditional reactions.
