index.js
function inheritGulp() {
  function TaskDoc() {
    this.taskList = new TaskList();
    gulp.Gulp.call(this);
  }
  TaskDoc.prototype = gulp;
  return new TaskDoc();
}
function inheritGulp() {
  function TaskDoc() {
    this.taskList = new TaskList();
    gulp.Gulp.call(this);
  }
  TaskDoc.prototype = gulp;
  return new TaskDoc();
}
Return a new instance that is inherited from Gulp
@returns {TaskDoc}