fix generators template bug

Author: regonn

lib/generators/serializer/templates/serializer.rb

@@ -1,8 +1,8 @@
 <% module_namespacing do -%>
 class <%= class_name %>Serializer < <%= parent_class_name %>
   attributes <%= attributes_names.map(&:inspect).join(", ") %>
-end
 <% association_names.each do |attribute| -%>
   has_one :<%= attribute %>
 <% end -%>
+end
 <% end -%>