Remove extra dimension in FlatObsWrapper. In response to #86.

gym_minigrid/wrappers.py

@@ -265,7 +265,7 @@ class FlatObsWrapper(gym.core.ObservationWrapper):
         self.observation_space = spaces.Box(
             low=0,
             high=255,
-            shape=(1, imgSize + self.numCharCodes * self.maxStrLen),
+            shape=(imgSize + self.numCharCodes * self.maxStrLen,),
             dtype='uint8'
         )