PEP-8 Fixes in algorithmic environment (#1382)

Remove trailing whitespaces.
Make line breaks adhere to 80 character limit (not all, but quite a few).
Remove unused imports.
Other miscellaneous PEP-8 fixes.

gym/envs/algorithmic/reverse.py

@@ -2,11 +2,12 @@
 Task is to reverse content over the input tape.
 http://arxiv.org/abs/1511.07275
 """
-
 from gym.envs.algorithmic import algorithmic_env
 
+
 class ReverseEnv(algorithmic_env.TapeAlgorithmicEnv):
     MIN_REWARD_SHORTFALL_FOR_PROMOTION = -.1
+
     def __init__(self, base=2):
         super(ReverseEnv, self).__init__(base=base, chars=True, starting_min_length=1)
         self.last = 50