QuadTree

A simple QuadTree implementation

So basically here I've got a bunch of objects all
colliding with each other using a QuadTree to optimise
the process

I'm pretty certain this isn't the fastest implementation
though. I can only push about 500 around

Plus you'll notice that when on intersections, things
get pretty piss poor. But it's much faster than a straight
comparison between all objects on screen, so there you
go...

@author Aaron Steed, nitrome.com