Added better support for mobile devices

- Added visual controls suitable for touchscreens.
- Changed level format to JSON for better portability.
This is to make it work with PGS4A (Pygame Subset for Android)
which doesn't bundle any XML module but does support json.
- Font path is now based on config.dataPath
- Added BACKSPACE as quit key and S as down key
- Added exit screen

README

@@ -5,7 +5,28 @@ Node Reviver was developed by Vincent Petry <PVince81@yahoo.fr> for MiniLD #33.
 Website: http://vincentpetry.net/games/nodereviver
 GitHub: http://github.com/PVince81/nodereviver
 
-This game was written in Python and uses Pygame internally.
+This game was written in Python and uses Pygame.
+
+
+Requirements
+------------
+
+- Pygame
+- To run on Maemo (Nokia N900), requires python-simplejson
+
+
+Running
+-------
+
+To start the game, simply run
+
+./nodereviver.py
+
+
+If using a mobile device without keyboard, you can enable touch screen
+support and fullscreen mode by adding this:
+
+./nodereviver.py --controls --fullscreen
 
 
 Game Rules