Added ability to disable serialization for a controller

This would allow a user to disable serialization for a specific controller by using the `disable_serialization` method in that controller. 

I believe that this can be useful for an application that creates an API that wraps an external services' API, i.e. Mailchimp. 

A real world example: I am creating an application that uses internal models such as User and Member and renders them in JSON using a serializer, as well as using Mailchimp's API and returning the data from them. The data returned from the Mailchimp API doesn't need a ActiveModel serializer, so this method is useful for disabling serialization in the controller the serves the Mailchimp API data.