Add AMS support to AR objects

lib/active_model_serializers.rb

@@ -11,3 +11,9 @@ begin
 rescue LoadError
   # rails not installed, continuing
 end
+
+[:active_record, :mongoid].each do |orm|
+  ActiveSupport.on_load(orm) do
+    include ActiveModel::SerializerSupport
+  end
+end