dist/multiplex.js
function promisify(fn) {
  return new Promise(function (resolve, reject) {
    fn(function (err, value) {
      if (err) reject(err);else resolve(value);
    });
  });
}
function promisify(fn) {
  return new Promise(function (resolve, reject) {
    fn(function (err, value) {
      if (err) reject(err);else resolve(value);
    });
  });
}
Simple promisify