Update the pip wheel in example.yaml and add docs (#1381)

python/ray/autoscaler/aws/example.yaml

@@ -3,7 +3,7 @@ cluster_name: default
 
 # The minimum number of workers nodes to launch in addition to the head
 # node. This number should be >= 0.
-min_workers: 0
+min_workers: 2
 
 # The maximum number of workers nodes to launch in addition to the head
 # node. This takes precedence over min_workers.
@@ -70,8 +70,7 @@ setup_commands:
     # Note: if you're developing Ray, you probably want to create an AMI that
     # has your Ray repo pre-cloned. Then, you can replace the pip installs
     # below with a git checkout <your_sha> (and possibly a recompile).
-    # TODO(ekl) update this to a wheel from master
-    - pip install -U https://s3-us-west-2.amazonaws.com/ray-wheels/f5ea44338eca392df3a868035df3901829cc2ca1/ray-0.3.0-cp36-cp36m-manylinux1_x86_64.whl
+    - pip install -U https://s3-us-west-2.amazonaws.com/ray-wheels/b6c42f96beab3ee00fe4b246e5e9d0479ad379ca/ray-0.3.0-cp36-cp36m-manylinux1_x86_64.whl
 
 # Custom commands that will be run on the head node after common setup.
 head_setup_commands: