Switched response queue to be a serial queue

Fixed the tvOS image size in the example

Example/tvOS Example/ViewController.swift

@@ -60,7 +60,7 @@ class CollectionViewCell : UICollectionViewCell {
     }
 
     func update(forGravatar gravatar:Gravatar) {
-        self.avatarView.setImageWithURL(gravatar.URL(size: self.avatarView.bounds.size.width))
+        self.avatarView.setImageWithURL(gravatar.URL(size: self.bounds.size.width))
     }
 }
 

UIKit+AFNetworking/AFImageDownloader.m

@@ -156,7 +156,7 @@
         self.activeRequestCount = 0;
 
         NSString *name = [NSString stringWithFormat:@"com.alamofire.imagedownloader.synchronizationqueue-%@", [[NSUUID UUID] UUIDString]];
-        self.synchronizationQueue = dispatch_queue_create([name cStringUsingEncoding:NSASCIIStringEncoding], DISPATCH_QUEUE_CONCURRENT);
+        self.synchronizationQueue = dispatch_queue_create([name cStringUsingEncoding:NSASCIIStringEncoding], DISPATCH_QUEUE_SERIAL);
 
         name = [NSString stringWithFormat:@"com.alamofire.imagedownloader.responsequeue-%@", [[NSUUID UUID] UUIDString]];
         self.responseQueue = dispatch_queue_create([name cStringUsingEncoding:NSASCIIStringEncoding], DISPATCH_QUEUE_CONCURRENT);