Add :delete semantics to iptables rules.

This wipes out all the relevant node attributes before every chef-client
run, so that the firewall rules will be updated if the attributes change
at all.
Ignore Foodcritic rule FC014.

Don't fail on FC014, since we have a ruby block longer than 15 lines,
where much of the code is comments and logging.
Merge pull request #34 from rtkmparrott/delete_old_rules

Add :delete semantics to iptables rules.