Added the underscore node_module.

node_modules/underscore/cjs/flatten.js

@@ -0,0 +1,9 @@
+var _flatten = require('./_flatten.js');
+
+// Flatten out an array, either recursively (by default), or up to `depth`.
+// Passing `true` or `false` as `depth` means `1` or `Infinity`, respectively.
+function flatten(array, depth) {
+  return _flatten(array, depth, false);
+}
+
+module.exports = flatten;