install gulp to process code

node_modules/arr-flatten/index.js

@@ -0,0 +1,22 @@
+/*!
+ * arr-flatten <https://github.com/jonschlinkert/arr-flatten>
+ *
+ * Copyright (c) 2014-2017, Jon Schlinkert.
+ * Released under the MIT License.
+ */
+
+'use strict';
+
+module.exports = function (arr) {
+  return flat(arr, []);
+};
+
+function flat(arr, res) {
+  var i = 0, cur;
+  var len = arr.length;
+  for (; i < len; i++) {
+    cur = arr[i];
+    Array.isArray(cur) ? flat(cur, res) : res.push(cur);
+  }
+  return res;
+}