How can I use the Pay Button with iOS Deployment Target 5.1.1?

The Pay Button runs on iOS 7 and up. However, you can still compile your app with a deployment target of iOS 5.1.1 and disable the payment functionality on devices below iOS 7. Remove the following lines from MPProvider.h:

#pragma mark -
#pragma mark Callback queue
/**
 * Dispatch queue used for block callbacks. If not set (NULL), dispatch_get_main_queue() will be used.
 * @since 2.0.0
 */
@property (strong, nonatomic) dispatch_queue_t callbackQueue;