A first stab at a pull-based model for ansible.  This does two things:
    1. Invoke the git module via Runner to set up a git repository on the
       localhost.  It sets up Runner to use transport='local' and forces
       the inventory to just 'localhost'.
    2. Run any playbooks provided.  By default, this wants to run the
       playbook local.yml.  This also sets transport='local' and sets
       the host_list to a list: localhost, fqdn, and hostname.
The reason for setting the host_list and not using override_hosts is
because there may be plays in the playbook that are not meant for a
specific host.  That is, if the git repository is for the entire site
and not host-specific, you don't want to override hosts and apply all
plays to any given host.  This has the downside of potentially running a
play three times if the play is defined for 'hosts: all'.