fix bug in the random agent example script (#9)
fix bug in the random agent example script (#9)

* fix bug in the random agent example script

When I ran the original script I got 

```
Logging to /tmp/openai-2018-12-14-17-36-08-425220
make: Entering directory '/home/act65/repos/coinrun/coinrun'
make: Nothing to be done for 'all'.
make: Leaving directory '/home/act65/repos/coinrun/coinrun'
Traceback (most recent call last):
  File "main.py", line 6, in <module>
    env = make('standard', num_envs=16)
  File "/home/act65/repos/coinrun/coinrun/coinrunenv.py", line 216, in make
    return CoinRunVecEnv(env_id, num_envs, **kwargs)
  File "/home/act65/repos/coinrun/coinrun/coinrunenv.py", line 156, in __init__
    obs_space = gym.spaces.Box(0, 255, shape=[self.RES_H, self.RES_W, num_channels], dtype=np.uint8)
AttributeError: module 'gym' has no attribute 'spaces'
```

Adding `import gym.spaces` fixes the bug ([see issue here](https://github.com/openai/gym/issues/376)). Although maybe it should be imported elsewhere!?

* moved import gym.spaces to coinrunenv.py

* moved import gym.spaces to coinrunenv.py

openai/coinrun,openai/coinrun