WIP: Captive portal iptables

*This code is currently NOT  ready for merging, and probably won't even work when you try to run the playbooks.*

This branch is based on the hackathon branch and has two goals:

1. Clean up the hackathon code so that it can be merged into master
1. Implement a better captive portal solution than the DNS wildcard solution used at the hackathon
  * Currently basing the system on [this](http://www.andybev.com/index.php/Using_iptables_and_PHP_to_create_a_captive_portal)