Various cleanups: remove start_ray_local from ray.init, remove unused code, fix "pip install numbuf". (#193)

* Remove start_ray_local from ray.init and change default number of workers to 10.

* Remove alexnet example.

* Move array methods to experimental.

* Remove TRPO example.

* Remove old files.

* Compile plasma when we build numbuf.

* Address comments.

doc/serialization.md

@@ -76,7 +76,7 @@ This can be addressed by calling `ray.register_class(Foo)`.
 ```python
 import ray
 
-ray.init(start_ray_local=True, num_workers=1)
+ray.init(num_workers=10)
 
 # Define a custom class.
 class Foo(object):