Fix readme to match current cookbook logic
Fix readme to match current cookbook logic

Doesn't expect the rule template name to start with `port_` anymore.
jmanero/iptables,patcon/iptables,jeffrafter/iptables,Altiscale/iptables,gt28/jtu_test,gt28/jtu_test,Altiscale/iptables,patcon/iptables,opscode-cookbooks/iptables,chef-cookbooks/iptables,czeeb/iptables,som3guy/iptables,czeeb/iptables,patcon/iptables,ashumski/iptables,chef-cookbooks/iptables,ashumski/iptables,alexdglover/iptables,opscode-cookbooks/iptables,som3guy/iptables,opscode-cookbooks/iptables,damienmg/iptables,gt28/jtu_test,chef-cookbooks/iptables,mjmeintjes/iptables,czeeb/iptables,ashumski/iptables,dldinternet/iptables,Altiscale/iptables,som3guy/iptables