using stateconf to include and extend for parameterized firewall control

Hi.

This pull request may not be so useful, but I want to give you the chance to decide.

I made a new state called `iptables.service` that can be included and extended in other state files. It was frustrating that pillar doesn't merge dictionaries, so I figured out this method to allow me to define a default firewall config in pillar and extend it in other pillars for systems with different firewall requirements. This is documented in the README.md.

I also fixed the pkg section to handle the RedHat os_family, and added a comment to the iptables rules.