hide away IP pool things in the UI if not enabled

app/views/servers/_form.html.haml

@@ -21,12 +21,13 @@
           outgoing & incoming mail will be held and only visible in the web interface and will not be
           sent to any recipients or HTTP endpoints.
 
-    .fieldSet__field
-      = f.label :ip_pool_id, :class => 'fieldSet__label'
-      .fieldSet__input
-        = f.collection_select :ip_pool_id, organization.ip_pools.includes(:ip_addresses).order("`default` desc, name asc"), :id, :description, {}, :class => 'input input--select'
-        %p.fieldSet__text
-          This is the set of IP addresses which outbound e-mails will be delivered from.
+    - if Postal.ip_pools?
+      .fieldSet__field
+        = f.label :ip_pool_id, :class => 'fieldSet__label'
+        .fieldSet__input
+          = f.collection_select :ip_pool_id, organization.ip_pools.includes(:ip_addresses).order("`default` desc, name asc"), :id, :description, {}, :class => 'input input--select'
+          %p.fieldSet__text
+            This is the set of IP addresses which outbound e-mails will be delivered from.
 
     - if @server.persisted?
       .fieldSet__field