code: function() {
          return new Promise(function(resolve, reject) {
              VkSdkLoginManager.authorize(function(error, result) {
                  if (error) {
                      reject(error);
                  } else {
                      resolve(result);
                  }
              });
          });
      }
docs: Starts authorization process to retrieve unlimited token.
  If VKapp is available in system, it will opens and requests access from user.
  Otherwise Mobile Safari will be opened for access request.
  @returns {Promise}