Add node modules and new code for release (#57)

Co-authored-by: taakleton <taakleton@users.noreply.github.com>

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;