ActiveRecord::RecordNotFound modified to store model name, primary_key
and id of the caller model. It allows the catcher of this exception to make
a better decision to what to do with it. For example consider this simple
example:

    class SomeAbstractController < ActionController::Base
      rescue_from ActiveRecord::RecordNotFound, with: :redirect_to_404

      private def redirect_to_404(e)
        return redirect_to(posts_url) if e.model == 'Post'
        raise
      end
    end