* Recursively check for nested gym.spaces.Dict objects in observation_space.spaces
* add tests; support nested tuples; asserts for dtype and space
* support for observation ravel, and more comprehensive tests
* cleanup print
* Updated spaces.py method description
No longer sampling from uniform distribution always, changing distribution
* update space.py sampling method description
* Added support for unbounded box endpoints.
* Documentation and code cleanup.
* Fixed some of the logic of upper bounded versus lower bounded spaces.
* Included unbounded Box instances for the original tests.
* Removed unnecessary attribute in the Box class.
* Added pendulumV2 with SI units
* Added pendulumV2 with SI units
* Fix gravity constant
* Delete pendulumV2.py
* Update pendulum.py
* Update pendulum.py
* Update pendulum.py
* 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
