Added movement between tiles.

Very basic movement between tiles. I've described the layout of the map in a json file (moving to x,y named files later should be simple if we want to do that. I didn't want to mess anybody up by changing the tile file names)

I had to modify some of the tmx files to add the different layers expected by the Tile class. I just duplicated the "Background" layer for all of the relevant tmx files I used in my sample map. To run it, just run movement.py 

I had to symlink cs429 into the game/src directory to get tile.py to not complain. There's probably a python interpreter option for that, though.