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

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

node_modules/underscore/cjs/invert.js

@@ -0,0 +1,13 @@
+var keys = require('./keys.js');
+
+// Invert the keys and values of an object. The values must be serializable.
+function invert(obj) {
+  var result = {};
+  var _keys = keys(obj);
+  for (var i = 0, length = _keys.length; i < length; i++) {
+    result[obj[_keys[i]]] = _keys[i];
+  }
+  return result;
+}
+
+module.exports = invert;