Entity and enemies

hero and enemies now extend the Entity superclass.  Mulitiple enemies are now showing via populateEnemies(). Collision detection has not been added yet. coming soon!!
This subroutine looks great! When this request is merged, I'll be able to extend this to use Tiled for placing the thugs through the object group features. And when I do, all I'll have to do is drop them into that array!