It seems iptables was removed in favor of [firewalld](http://fedoraproject.org/wiki/Features/firewalld-default) in Fedora 18.  Would it make sense to say Fedora 18 and up are unsupported until a `firewalld` provider is implemented?  I'd be happy to work on a pull request for that and amend this one so it will `fail` on Fedora 18+.