Updated requirements.txt with specific version numbers of the packages

[SaurabhAgarwala]

Resolves Issue #14

Version numbers for the required packages in requirements.txt are specified, without which incompatible version of packages - gym(0.15.3), tensorflow(2.0.0) gets installed and throws up error while execution. No version for numpy has been specified as even the latest version (1.17.3)as of today is compatible with the project.

Checklist

• [x] Code compiles correctly.
• [x] Changes are tested properly.
• [x] Added the README / documentation

[johnny-wang16]

Acutally the dependencies are specified in the README. I tried your requirements.txt and it didnt work. specifically gym version needs to be 0.9.1 and tensorflow needs to be 1.1.0 otherwise you would get import error from tensorflow and mujoco-py. ''' Python version 3.6 OpenAI GYM version 0.9.1 with MuJoCo 1.31 support (use mujoco-py version 0.5.7) Tensorflow version 1.1.0 Numpy version 1.12.1 '''