updated load and save function. Now also distance maps are stored.

Additional package msgpack-numpy needed for ndarray.
This saves tons of time when loading precomputed files.
Updated test to test loading and saving with and without distance maps
minor update to bug in observation dimension
fixed typos

flatland/envs/observations.py

@@ -22,8 +22,6 @@ class TreeObsForRailEnv(ObservationBuilder):
     For details about the features in the tree observation see the get() function.
     """
 
-
-
     def __init__(self, max_depth, predictor=None):
         super().__init__()
         self.max_depth = max_depth