big update

-removed unimplemented ST_Text class for now
-pixel perfect collision kind of sort of fixed
--accounted for supersprite local space
--accounted for spritesheet origin point
--didn't account for rotated sprites
-added "superSprite" boolean ST_Detachment property (doesn't actually
help a whole lot, since if you know that the object is a detachment, you
probably know whether it's a sprite)
-shrunk our one enemy
-fixed draw() inconsistencies
-fixed bullet recycling issue (sprites weren't drawing after reset
because the graphics object was cleared and play was set to false,
preventing a new draw)
-made player/enemy origins centered