Collision Tutorial 1st draft

Hey man!

So I did a basic collision tutorial - I still need to clean it up, fix the member variable prefixes (i used mVar instead of m_Var XD), remove some debug lines, and document a little more.  There's one problem that I can't figure out - for some reason, the sprites are getting rendered half of their width to the right; but their bounding boxes are at the correct position.  If you don't see anything right away, don't worry about it - I'll probably be able to get down to the bottom of it within a couple of days.

Anyway, tell me if you see anything glaringly wrong in the Game.cpp - I followed your convention layed out in the Movement tutorial, and made Game inherit from CollisionSystem::Listener and overrode the CollisionSystem::Listener function.  In the original source, you didn't have the onCollisionOccured function an absolute virtual - I made it so; is there a reason you didn't?