create/update/destroy can now have custom events

I allows you to have custom events, this is useful when you want to track specific changes with a specific name, let's say that you have a model 'Sale' with some fields like 'price' 'sale_price', and you want to use an specific event when the 'price' changes, so you use something like:

    class Sale
      before_update :set_custom_event
      has_paper_clip
      
      private
      def set_custom_event
        self.custom_event = 'price_changed' if price_changed?
      end
    end