Refactor of 'ferm' role

- you can now change or disable the comment that is added ad the
  beginning of iptables rules;

- you can define default INPUT, OUTPUT and FORWARD chain policy via
  Ansible variables;

- you can use templates to easily create iptables rules in inventory
  variables or role dependencies;

- access to ssh from Ansible Controller should not be constantly enabled
  and disabled anymore while running roles via Ansible tags;

- when these changes are applied, access to http and https ports will be
  disabled by default, and access to ssh will be allowed only from Ansible
  Controller host. These rules will be changed later via respective roles
  (sshd, nginx);
Merge pull request #29 from drybjed/role/ferm

Refactor of 'ferm' role