Mujoco envs

[cathywu]

Summary [exp cluster-HumanoidStandup-comparison-v0]

• Testing on this env because this is the env with the largest action space among the Mujoco envs (k=17), though still small.
• There's a small regression of performance between GaussianMLP baseline and AD GaussianMLP baseline. (What might cause this regression?)

HumanoidStandup-v1, batch_size=10000, baseline_include_time=False: HumanoidStandup-v1, batch_size=25000, baseline_include_time=False: