Ansible touchups

This addresses a few issues with the production and staging Ansible playbooks. Specifically, it puts `localhost` in a group of its own, `local`, and restricts local operations to that group. This keeps Ansible from provisioning `localhost` like a webserver and doing other odd things (#316).

I did still need to add an `ansible_python_interpreter` variable to localhost to actually run it.
Heh, I keep stashing this whitespace change.