Allow using to-port option

iptables/_rule.sls

@@ -38,6 +38,9 @@ iptables_{{ chain_name }}_{{ rule_name }}:
   {%- if rule.to_destination is defined %}
   - to-destination: {{ rule.to_destination }}
   {%- endif %}
+  {%- if rule.to_port is defined %}
+  - to-port: {{ rule.to_port }}
+  {%- endif %}
   {%- if rule.to_source is defined %}
   - to-source: {{ rule.to_source }}
   {%- endif %}