func purchases(Purchases, receivedUpdated : CustomerInfo ) Called whenever
Purchases receives updated customer info. This may happen periodically throughout the life of the app if new information becomes available (e.g. UIApplicationDidBecomeActive).*func purchases(Purchases, shouldPurchasePromoProduct : StoreProduct , defermentBlock : DeferredPromotionalPurchaseBlock ) Called when a user initiates a promotional in-app purchase from the App Store. If your app is able to handle a purchase at the current time, run the deferment block in this method. If the app is not in a state to make a purchase: cache the defermentBlock, then call the defermentBlock when the app is ready to make the promotional purchase. If the purchase should never be made, you don’t need to ever call the defermentBlock and
Purchases will not proceed with promotional purchases.