code: public static RequestToken fetchAll(BaasHandler<List<BaasUser>> handler) {
          return fetchAll(null, RequestOptions.DEFAULT, handler);
      }
docs: Asynchronously fetches the list of users from the server.
  
  @param handler an handler to be invoked upon completion of the request
  @return a {@link com.baasbox.android.RequestToken} to manage the request