This performs a similar function to oauth_listener()
,
but without running a local webserver. This manual process can be useful
in situations where the user is remotely accessing the machine outside a
browser (say via ssh) or when it's not possible to successfully receive a
callback (such as when behind a firewall).
oauth_exchanger(request_url)
the url to provide to the user
This function should generally not be called directly by the user.