Ensure we call authorize! :admin in admin controllers
Correct references to spree_auth_devise in spree_cmd/installer and sanbdox script
Remove ShippingMethod#displayable?

This method doesn't appear to be acted on anywhere inside Spree's code, thereby making it useless
Remove ancient comment for Zone#include?
Remove Payment#promo_total

We have this information from the Order model. We can just access it from there, just like we do with item_total, ship_total and tax_total
Added CouponApplicator class

This is used within API's CheckoutsController and frontend's CheckoutController
and OrdersController.