Removed spawn method from world

Reconsidering how to spawn objects so for now this will be removed.
Removed dead code from Hero, made update safer

The update method assumes that the hero is in a room. If his room
pointer is null then he blows up when you update him. Added a null check
for room within update();
Made SpriteAnimator safer

Missing a check for null; if animation pointer was null then things blow
up.
Changed spawned enemy positions
Added hero and map rendering to GamePlayState
Merge pull request #16 from zackthehuman/master

Code cleanup, fixing null pointer checks, moving code around