Add :use_rule_comments option

If set, iptables commands have -m comment --comment "Rule Name Here"
added, resulting in iptables -L output like this:

ACCEPT tcp -- 10.1.2.3 anywhere tcp dpt:http ctstate NEW /* Allow all HTTP */
set default use_rule_comments = true
Merge branch 'add-iptables-comments' of github.com:irccloud/AFW
Bump to v0.0.6