refactoring to move calculations from views to models.  moved the PartneredItem.price_after_percentage to PartmeredItem.calculate_price_after_percentage() as a helper method to calculate the price and delivery fee
refactoring from views to models.  created a Delivery.find_deliveries(date, user) to get all the deliveries needed for the delivery_manager page
refactored a search built into SimpleContact as a @staticmethod
created a Delivery.ready_for_delivery @property