code: function addMdExts () {
    var args = Array.prototype.slice.call(arguments);
    return args.reduce(function (memo, item) {
      return memo.concat([
        item + '.md',
        item + '.mkdn',
        item + '.mdown',
        item + '.markdown'
      ]);
    }, []);
  }
docs: ## `addMdExts` add various markdown extensions to the given arguments ### `arguments` arguments to add markdown extensions to