Added the underscore node_module.

node_modules/underscore/amd/flatten.js

@@ -0,0 +1,11 @@
+define(['./_flatten'], function (_flatten) {
+
+  // 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);
+  }
+
+  return flatten;
+
+});