Remove register_class from API. (#550)

* Perform ray.register_class under the hood.

* Fix bug.

* Release worker lock when waiting for imports to arrive in get.

* Remove calls to register_class from examples and tests.

* Clear serialization state between tests.

* Fix bug and add test for multiple custom classes with same name.

* Fix failure test.

* Fix linting and cleanups to python code.

* Fixes to documentation.

* Implement recursion depth for recursively registering classes.

* Fix linting.

* Push warning to user if waiting for class for too long.

* Fix typos.

* Don't export FunctionToRun if pickling the function fails.

* Don't broadcast class definition when pickling class.

examples/evolution_strategies/evolution_strategies.py

@@ -154,10 +154,6 @@ if __name__ == "__main__":
   ray.init(redis_address=args.redis_address,
            num_workers=(0 if args.redis_address is None else None))
 
-  # Tell Ray to serialize Config and Result objects.
-  ray.register_class(Config)
-  ray.register_class(Result)
-
   config = Config(l2coeff=0.005,
                   noise_stdev=0.02,
                   episodes_per_batch=10000,

examples/policy_gradient/examples/example.py

@@ -33,10 +33,6 @@ if __name__ == "__main__":
 
   ray.init(redis_address=args.redis_address)
 
-  ray.register_class(AtariRamPreprocessor)
-  ray.register_class(AtariPixelPreprocessor)
-  ray.register_class(NoPreprocessor)
-
   mdp_name = args.environment
   if args.environment == "Pong-v0":
     preprocessor = AtariPixelPreprocessor()