docs: function promisedRequest(params, callback) {
    var deferred = Promise.defer();
    var req;
    var createRequest = function() {
      if (!req) {
        req = request(params, function(err, response) {
          if (err) {
            deferred.reject(err);
          } else {
            deferred.resolve(response);
          }
        });
      }
      return req;
    };
    return streamify(deferred.promise, createRequest).thenCall(callback);
  }