gh: Auth fix

@mislav I'm trying to get [this cuke](https://github.com/github/hub/blob/master/features/authentication.feature#L170-L204) passing. But the expectation seems wrong to me as I mentioned [here](https://github.com/github/hub/pull/515#issuecomment-38505634):

> I would expect the access token to be "OTOKEN" instead of "OTOKENSMS", because the first GET for authorizations, the server returns 401 and asks for OTP, the second GET for authorizations will be successful and return the access token. That says, it never POST to create authorizations which adds the "SMS" part. I might be missing some details though.