Modified all the NSURLSessionDownloadDelegate methods to first call the override closures.

Source/Alamofire.swift

@@ -522,27 +522,27 @@ public class Manager {
         public var downloadTaskDidResumeAtOffset: ((NSURLSession!, NSURLSessionDownloadTask!, Int64, Int64) -> Void)?
 
         public func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didFinishDownloadingToURL location: NSURL) {
-            if let delegate = self[downloadTask] as? Request.DownloadTaskDelegate {
+            if downloadTaskDidFinishDownloadingToURL != nil {
+                downloadTaskDidFinishDownloadingToURL!(session, downloadTask, location)
+            } else if let delegate = self[downloadTask] as? Request.DownloadTaskDelegate {
                 delegate.URLSession(session, downloadTask: downloadTask, didFinishDownloadingToURL: location)
             }
-
-            downloadTaskDidFinishDownloadingToURL?(session, downloadTask, location)
         }
 
         public func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {
-            if let delegate = self[downloadTask] as? Request.DownloadTaskDelegate {
+            if downloadTaskDidWriteData != nil {
+                downloadTaskDidWriteData!(session, downloadTask, bytesWritten, totalBytesWritten, totalBytesExpectedToWrite)
+            } else if let delegate = self[downloadTask] as? Request.DownloadTaskDelegate {
                 delegate.URLSession(session, downloadTask: downloadTask, didWriteData: bytesWritten, totalBytesWritten: totalBytesWritten, totalBytesExpectedToWrite: totalBytesExpectedToWrite)
             }
-
-            downloadTaskDidWriteData?(session, downloadTask, bytesWritten, totalBytesWritten, totalBytesExpectedToWrite)
         }
 
         public func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didResumeAtOffset fileOffset: Int64, expectedTotalBytes: Int64) {
-            if let delegate = self[downloadTask] as? Request.DownloadTaskDelegate {
+            if downloadTaskDidResumeAtOffset != nil {
+                downloadTaskDidResumeAtOffset!(session, downloadTask, fileOffset, expectedTotalBytes)
+            } else if let delegate = self[downloadTask] as? Request.DownloadTaskDelegate {
                 delegate.URLSession(session, downloadTask: downloadTask, didResumeAtOffset: fileOffset, expectedTotalBytes: expectedTotalBytes)
             }
-
-            downloadTaskDidResumeAtOffset?(session, downloadTask, fileOffset, expectedTotalBytes)
         }
 
         // MARK: NSObject