Show supporter level ticket URL on the registration page

app/views/conference_registration/register.html.haml

@@ -27,10 +27,19 @@
         - if @conference.use_supporter_levels?
           = f.semantic_fields_for :supporter_registration do |reg|
             = reg.input :supporter_level, :as => :select, :collection => @conference.supporter_levels
-            = reg.input :code, :hint => "If you have a confirmation or registration code, enter it here."
+            = reg.input :code, :label => "Confirmation or registration code (if applicable)"
+            %span#supporter-link.help-block
         - if @registered
           = f.action :submit, :button_html => { :value => "Update Registration", :class => "btn btn-primary" }
           = link_to "Unregister", register_conference_path(@conference.short_title),:method => :delete, :class => "btn btn-danger",
                       :confirm => "Are you sure you want to unregister?"
         - else
           = f.action :submit, :button_html => { :value => "Register", :class => "btn btn-primary" }
+
+:javascript
+    $("#registration_supporter_registration_attributes_supporter_level_id").change(function () {
+      var str = "";
+      #{generate_supporter_level_js @conference}
+      $("#supporter-link").html(str);
+    })
+    .trigger('change');