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.

test/stress_tests.py

@@ -65,7 +65,7 @@ class TaskTests(unittest.TestCase):
         ray.worker.cleanup()
 
   def testGettingAndPutting(self):
-    ray.init(start_ray_local=True, num_workers=1)
+    ray.init(num_workers=1)
 
     for n in range(8):
       x = np.zeros(10 ** n)