FOV

-Moved rendering of enemies into the world which owns the enemies.
-Draw the floor with a period tile.  This looks better with FOV turned
on.
-Light callback and fov code.  Only render visible tiles in the world
and only enemies that are visible.  Ideally it would be nice to have a
has from position -> enemy that way I wouldn't have to cache visible
tiles and then iterate each enemy later.
-remove worldbuilder console.log