Automatic merge from submit-queue

Added instructions on turning on dynamic provisioning for testing.

HostPath volumes are not automatically provisioned unless we pass in `--enable-hostpath-provisioner` to the controller manager. This was not mentioned in the docs previously, leading to questions like [this](https://groups.google.com/forum/#!searchin/kubernetes-dev/mysterious/kubernetes-dev/jVk_RgAkbaY/LRX7IuCEDQAJ).