Example code doesn't converge

[Omegastick]

Some time around ae03039 we regressed and the example code in gym_client.cpp doesn't converge any more. Presumably because of some difference in our observation normalization compared to the OpenAI Baselines one.

I'll look in more detail this weekend and confirm if it's that exact commit causing the problem.

[Omegastick]

After fixing #14, it converges, but I feel like it used to converge faster. I'll run some more detailed comparisons when I get time.

FPS has dropped about 20% on my laptop since the first release, but that could be a lot of things.