Vectorized environments (#1513)

* Initial version of vectorized environments

* Raise an exception in the main process if child process raises an exception

* Add list of exposed functions in vector module

* Use deepcopy instead of np.copy

* Add documentation for vector utils

* Add tests for copy in AsyncVectorEnv

* Add example in documentation for batch_space

* Add cloudpickle dependency in setup.py

* Fix __del__ in VectorEnv

* Check if all observation spaces are equal in AsyncVectorEnv

* Check if all observation spaces are equal in SyncVectorEnv

* Fix spaces non equality in SyncVectorEnv for Python 2

* Handle None parameter in create_empty_array

* Fix check_observation_space with spaces equality

* Raise an exception when operations are out of order in AsyncVectorEnv

* Add version requirement for cloudpickle

* Use a state instead of binary flags in AsyncVectorEnv

* Use numpy.zeros when initializing observations in vectorized environments

* Remove poll from public API in AsyncVectorEnv

* Remove close_extras from VectorEnv

* Add test between AsyncVectorEnv and SyncVectorEnv

* Remove close in check_observation_space

* Add documentation for seed and close

* Refactor exceptions for AsyncVectorEnv

* Close pipes if the environment raises an error

* Add tests for out of order operations

* Change default argument in create_empty_array to np.zeros

* Add get_attr and set_attr methods to VectorEnv

* Improve consistency in SyncVectorEnv

setup.py

@@ -31,7 +31,8 @@ setup(name='gym',
                 if package.startswith('gym')],
       zip_safe=False,
       install_requires=[
-          'scipy', 'numpy>=1.10.4', 'six', 'pyglet>=1.2.0',
+          'scipy', 'numpy>=1.10.4', 'six', 'pyglet>=1.2.0', 'cloudpickle~=1.2.0',
+          'enum34~=1.1.6;python_version<"3.4"'
       ],
       extras_require=extras,
       package_data={'gym': [