Started writing Entity class.
Finished Entity class.
The Entity class will serve as a wrapper for anything that has a sprite and unique properties that need to be kept track of (like the player, a monster, or a fireball). It's also a lot neater to write player.x than player.sprite.x.
Small cleanup of Tile class.
Made x and y local variables, since they're already properties of Entity.
Removed the obvious comment about updateOffset().