Change demo to PongDeterministic-v4

[jbn]

The demo as specified in the README requires a deprecated version of PongDeterministic. Running after a clean install on my computer results in:

Traceback (most recent call last):
  File "/Users/generativist/RL/external/gym/gym/envs/registration.py", line 137, in spec
    return self.env_specs[id]
KeyError: 'PongDeterministic-v3'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "worker.py", line 152, in <module>
    tf.app.run()
  File "/Users/generativist/anaconda/envs/odin/lib/python3.5/site-packages/tensorflow/python/platform/app.py", line 48, in run
    _sys.exit(main(_sys.argv[:1] + flags_passthrough))
  File "worker.py", line 144, in main
    run(args, server)
  File "worker.py", line 26, in run
    env = create_env(args.env_id, client_id=str(args.task), remotes=args.remotes)
  File "/Users/generativist/RL/external/universe-starter-agent/envs.py", line 18, in create_env
    spec = gym.spec(env_id)
  File "/Users/generativist/RL/external/gym/gym/envs/registration.py", line 164, in spec
    return registry.spec(id)
  File "/Users/generativist/RL/external/gym/gym/envs/registration.py", line 145, in spec
    raise error.DeprecatedEnv('Env {} not found (valid versions include {})'.format(id, matching_envs))
gym.error.DeprecatedEnv: Env PongDeterministic-v3 not found (valid versions include ['PongDeterministic-v4', 'PongDeterministic-v0'])

This output was produced by the window calling,

CUDA_VISIBLE_DEVICES= /Users/generativist/anaconda/envs/odin/bin/python worker.py --log-dir /tmp/pong --env-id PongDeterministic-v3 --num-workers 2 --visualise --job-name worker --task 0 --remotes 1

Changing to PongDeterministic-v4 worked.