Added player class and renamed bouncer to mobs.
Added moving player object. Key code printing.

The key code printing stuff is commented out and not working idealy as I'd like
it to. In the end it'll be unimportant but it's nice to quickly know what
keypresses are called. For know I'll just check pygame.K_*.

Known issue, the player does not continue moving if you hold down a key, it
only moves one SPEED unit for each key press.