Fixing a 2 bugs and 1 warning other forks seemed to have found.
Setting a AFURLSessionManagerTaskDelegate as an associated object on its NSURLSessionTask. This eliminates the need for the Session manager to keep track of the mapping from tasks to delegates with the mutableTaskDelegatesKeyedByTaskIdentifier dictionary. As a consequence, locks are no longer needed when setting or retrieving a delegate. The delegate is associated with a strong, nonatomic reference. Strong because this is the only reference to the delegate. Nonatomic because this value will never be read to and written to simultaneously.