code: function login (hubhost, hubport) {
    debug('login on hub ' + hubhost + (hubport ? ':' + hubport : ''))
    return loginToHub(hubhost, hubport)
  }
docs: Function: login
  Retrieves a UserAuthToken using a valid Harmony account and logs in to a
  local Harmony hub. If everything runs fine, the returned promise resolves by
  passing a logged in XMPP client which provied communications to the Hamrony
  hub.
  
  Parameters:
  (String) email - E-mail address of a Harmony account
  (String) password - Password of a Harmony account
  (String) hubhost - Hostname/IP of the Harmony hub to login to.
  (int) hubport - Optional. Port of the Harmony hub to login to.
  
  Returns:
  (Q.promise) - When resolved, the promise passes a prepared XMPP client,
  ready to communicate with the Harmony hub.