* Direction substitution of @ray.remote -> @ray.task.
* Changes to make '@ray.task' work.
* Instantiate actors with Class.remote() instead of Class().
* Convert actor instantiation in tests and examples from Class() to Class.remote().
* Change actor method invocation from object.method() to object.method.remote().
* Update tests and examples to invoke actor methods with .remote().
* Fix bugs in jenkins tests.
* Fix example applications.
* Change @ray.task back to @ray.remote.
* Changes to make @ray.actor -> @ray.remote work.
* Direct substitution of @ray.actor -> @ray.remote.
* Fixes.
* Raise exception if @ray.actor decorator is used.
* Simplify ActorMethod class.
