Expose timeout.

Expose `timeout` on `hipchat.method` so that it's safer to use synchronously on a path that shouldn't hang. Leaves current signature/behavior unchanged -- it would probably be a good idea to default the timeout to something reasonable, though.

(This is actually a pretty bad interface, but doesn't break existing code and it gets the job done.  Ideally you'd specify the timeout once, or make it easier to override the opener, or something, I guess.)