Update README with info about puppet apply
Update README with info about puppet apply

The README currently says you have to pass puppetmaster, but this is
untrue for puppet apply installs. Add an example playbook to run puppet
without a puppet master.

Change-Id: I6dfb5b97cbca42b83f790310b12a3d49f7dae8a0

openstack-infra/ansible-puppet,openstack-infra/ansible-puppet