Added the underscore node_module.

node_modules/underscore/amd/union.js

@@ -0,0 +1,11 @@
+define(['./restArguments', './uniq', './_flatten'], function (restArguments, uniq, _flatten) {
+
+  // Produce an array that contains the union: each distinct element from all of
+  // the passed-in arrays.
+  var union = restArguments(function(arrays) {
+    return uniq(_flatten(arrays, true, true));
+  });
+
+  return union;
+
+});