message: Impliment account-linking
diff: @@ -458,8 +458,12 @@ function Facebookbot(configuration) {
  };
  facebook_botkit.api.thread_settings.deleteAPI(message);
  },
  - account_linking: function() {
  -
  + account_linking: function(payload) {
  + var message = {
  + 'setting_type': 'account_linking',
  + 'account_linking_url': payload
  + };
  + facebook_botkit.api.thread_settings.postAPI(message);
  },
  postAPI: function(message) {
  request.post('https://graph.facebook.com/v2.6/me/thread_settings?access_token=' + configuration.access_token,
  