Upgrade to latest gym library

Problem:

There was a breaking change made to the gym library a couple months ago which is affecting the initialization of the environment. The gym library was at version 0.7.4 for a long time (almost a year) and was working fine. The latest version (0.9.6 - see here) includes the breaking change. This issue is to track updating the project to account for these breaking changes.

Changes required:

At least the following:

Multi-discrete action space needs to match the new format
The new format for the action space will likely require a shift of values (e.g. instead of [-80,80] it will be [0, 160], so need to add/subtract 80 to maintain current behavior)

Workaround:

In the meantime, to get up-and-running, just change two files in the base gym-mupen64plus directory:

environment.yml - line 16
setup.py - line 5

Each of them should have the gym library set explicitly to use the older version (gym=0.7.4 or gym==0.7.4), which should then behave as expected. The setup process may need to be re-run after making this change.

See #40 for the resulting broken behavior with the new version of gym.

bzier / gym-mupen64plus