Added the underscore node_module.

node_modules/underscore/cjs/union.js

@@ -0,0 +1,11 @@
+var restArguments = require('./restArguments.js');
+var uniq = require('./uniq.js');
+var _flatten = require('./_flatten.js');
+
+// 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));
+});
+
+module.exports = union;