Unsubscribe skPaymentQueue transactionObserver

fixes #165

Author: Hasan Turken

iOS_SDK/OneSignal/OneSignalTrackIAP.m

@@ -57,6 +57,12 @@ - (id)init {
     return self;
 }
 
+- (void)dealloc {
+  if (skPaymentQueue) {
+    [[skPaymentQueue performSelector:@selector(defaultQueue)] performSelector:@selector(removeTransactionObserver:) withObject:self];
+  }
+}
+
 - (void)paymentQueue:(id)queue updatedTransactions:(NSArray*)transactions {
     skusToTrack = [NSMutableDictionary new];
     id skPayment;