0, 0 coordinate is now in the center of the screen
Changed Adventurer's starting position in TestWorldFactory to 0,0.
Added StateMachine for entities.
Added constructor to StateMachine to keep track of the owner.
Added class comments to StateMachine.
Added Update method to StateMachine.
Added state class.
Added abstract methods to State.
Added CreeperSeeking state.
Added comments.
Added Creeper Wandering state
World.Entities is now public and _entities is now explicitly private.
Creeper now has a contsructor which takes a World object.
StateMachine now takes objects other than Entities.