Renamed method in private header to indicate that it is a private method.
Fixed bug where the addCompletionBlock method on FDRequestClientTask could be called but the completion block may never be called or its addition may even crash the app.

If addCompletionBlock was called while the completion blocks were being
iterated over it would cause a crash because the array would be
modified while being enumerated over.

If addCompletionBlock was called after the completion blocks were
iterated over then the completion block that was added would never been
called.
Fixed bug where the active tasks were not being dealloc'd when they completed.