Update atari-py from upstream ALE

[christopherhesse]

We should update the version of ALE used in atari-py to get at least the following changes:

• https://github.com/mgbellemare/Arcade-Learning-Environment/pull/265
• https://github.com/mgbellemare/Arcade-Learning-Environment/pull/264

This might be a good chance to re-structure the repo as a fork of ALE instead of manually updating.

[jkterry1]

Closed as Atari-Py has been deprecated in favor of ALE-Py