Added .DS_Store to .gitignore
Commented out wall-creating code from room and tunnel methods.  Will
test tonight.

Also simplified the tunneling method but abstracting out the horizontal
and vertical tunnel logic.  Should make this more complicated later by
selecting a random point on the wall of each room and connect those,
rather than going from the centers.
Modified tunnel methods to check whether any room generated so far
contains the tile to be tunnelled.  This should reduce some of the
overlap problem.
Added a method to fill in empty spaces in Level.TileArray with wall
tiles.  AddTile now only adds the tile to TileArray.  Added a loop to
add all of TileArray to self.tiles at the end of CreateRooms().