Expand the README.md.
Expand the README.md.

Added a note about not running this on production machines and how to
use it.

toabctl/openstack-quickstart,sjamgade/openstack-quickstart,wenhuizhang/openstack-quickstart,hayderimran7/openstack-quickstart,sayalilunkad/openstack-quickstart,vuntz/openstack-quickstart,SUSE-Cloud/openstack-quickstart