add the early stages of collision, we can now find out if the little man's touching another object on the screen
check collision on 4 points
don't let an entity move if it would collide with a collision type (wall)
only allow an entity to move up if they're on a ladder, and implement gravity in dude
merge master changes in collision branch
center justify the entity when moving up a ladder
dude logic entity->dude, minor tweaks
logic entity->dude