message: add get_account_linking
diff: @@ -470,6 +470,9 @@ function Facebookbot(configuration) {
  delete_account_linking: function () {
  facebook_botkit.api.messenger_profile.deleteAPI('account_linking_url');
  },
  + get_account_linking: function () {
  + facebook_botkit.api.messenger_profile.getAPI('account_linking_url');
  + },
  postAPI: function (message) {
  request.post('https://graph.facebook.com/v2.6/me/messenger_profile?access_token=' + configuration.access_token,
  {form: message},
  