This is mostly carryover from the previous version: I'm not too happy with it honestly. But I'll need to change the way the signing module works if we change it. Popping it isn't really necessary now that it's also being reset before it builds up the OAuth params. I think ideally we'd just pass these into the signing object and leave it at that. Really I'd like to completely decouple the singing from the Session/Service wrappers.