Changing Discrete Variables to Continuous Variables for More Algorithms

[smiret]

I changed the the MarsDiscreteEnv(MarsEnv) to produce continuous actions instead of the self.action_space = spaces.Discrete(3) which signals that the action space is discrete to the RL manager and thereby limits the implementation of continuous based RL algorithms. I have also added comments in my changes.

In the setup.py file of the rl-agent repo I changed the install to have newer version of gym and rl-coach to have access to a larger library of RL algorithms from RL coach.