message: Add callback to getAccountLinking
diff: @@ -479,8 +479,8 @@ 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');
  + get_account_linking: function(cb) {
  + facebook_botkit.api.messenger_profile.getAPI('account_linking_url', cb);
  },
  domain_whitelist: function(payload) {
  var message = {
  