Big Update

I've added in the game loop, which allows us to animate the objects.
I've also added in collisions with the walls, so objects don't
disappear.
Finally, I've put in keypress listening events, so now when you press
left or right you can move the paddle.
Next up is adding losing a life if the ball hits the floor, adding the
blocks and making the ball bounce (and register a hit) off the blocks
and paddle.