[Issue #241] Set HTTPBodyStream for streamed request

Signed-off-by: Mattt Thompson <m@mattt.me>

Source/Alamofire.swift

@@ -984,7 +984,7 @@ extension Manager {
 
     private func upload(uploadable: Uploadable) -> Request {
         var uploadTask: NSURLSessionUploadTask!
-        var stream: NSInputStream?
+        var HTTPBodyStream: NSInputStream?
 
         switch uploadable {
         case .Data(let request, let data):
@@ -993,12 +993,13 @@ extension Manager {
             uploadTask = session.uploadTaskWithRequest(request, fromFile: fileURL)
         case .Stream(let request, var stream):
             uploadTask = session.uploadTaskWithStreamedRequest(request)
+            HTTPBodyStream = stream
         }
 
         let request = Request(session: session, task: uploadTask)
-        if stream != nil {
+        if HTTPBodyStream != nil {
             request.delegate.taskNeedNewBodyStream = { _, _ in
-                return stream
+                return HTTPBodyStream
             }
         }
         delegate[request.delegate.task] = request.delegate