Don't show flash messages in customer edition form

They don't actually show up when the customer is saved, but the next
time the page is reloaded. We already have the save bar for the same
purpose so it's not necessary.

app/controllers/admin/customers_controller.rb

@@ -51,6 +51,18 @@ module Admin
       end
     end
 
+    # copy of Admin::ResourceController without flash notice
+    def update
+      if @object.update(permitted_resource_params)
+        respond_with(@object) do |format|
+          format.html { redirect_to location_after_save }
+          format.js   { render layout: false }
+        end
+      else
+        respond_with(@object)
+      end
+    end
+
     # copy of Admin::ResourceController without flash notice
     def destroy
       if @object.destroy