OK well, that's better I guess

For now... Mario is still clipping some of the time, through blocks, but
a lot of the time he is A OK
Debugging the wall stick

When Mario jumps, there is a special case in which lines that aught to
intersect are not doing so. In this case, the collision behaves in the
old way and bounces mario in the wrong direction.
The collision surface of the tile needs to be 1 pixel wider

I ran a missed collision through wolfram and noticed that it was missing
the collision (over or under shooting the tile). Moving the collision
wall by one pixel resolved this.
Fixed screen scroll to the edge of the world.
Added canExplore and bidirectional screen_scrolling

When mario.canExplore() is true, then mario can go backwards.
Backwards shrine now enables backwards ability
Mario starts in the right place on every map
Draw sky as a rectangle, midpoint according to map
No longer draw sky in love.draw
Got most bands working :)
Got the top two bands working