Non-implemented TUIO handlers no longer raise an exception.

src/tuio_server.py

@@ -80,13 +80,13 @@ class TuioServerHandler(object):
     handlers.
     """
     def on_point_down(self, sid, x, y):
-        raise NotImplementedError
+        return NotImplemented
 
     def on_point_move(self, sid, x, y):
-        raise NotImplementedError
+        return NotImplemented
 
     def on_point_up(self, sid):
-        raise NotImplementedError
+        return NotImplemented
 
 
 if __name__ == '__main__':