The current implementation of HTTPClient is mostly a direct port of its objective-c counterpart, but its logic is somewhat contrived, and it's not actually taking advantage of the two dispatchqueues it's managing.

This entire class could be refactored so that:

• it uses the corresponding queue to send stuff concurrently or serially
• its logic is simplified by leveraging the queue to, well, queue tasks, as oppposed to managing another queue of tasks manually