This will not save or flush current iptables rules so that it makes the
iptables-restore provider compatible with docker or similar software
that manage their own rules in iptables.

Closes: #2 

* add the option to specify the family per rule to support ipv6

* include policy updates for ipv6

* update documentation to mention ipv6

* Make ipv6 optional; remove spurious tabs from the readme.

* set ipv6 policies only if ipv6 is enabled on the host and not explicitly turned off for this service