Added the underscore node_module.

node_modules/underscore/cjs/keys.js

@@ -0,0 +1,18 @@
+var isObject = require('./isObject.js');
+var _setup = require('./_setup.js');
+var _has = require('./_has.js');
+var _collectNonEnumProps = require('./_collectNonEnumProps.js');
+
+// Retrieve the names of an object's own properties.
+// Delegates to **ECMAScript 5**'s native `Object.keys`.
+function keys(obj) {
+  if (!isObject(obj)) return [];
+  if (_setup.nativeKeys) return _setup.nativeKeys(obj);
+  var keys = [];
+  for (var key in obj) if (_has(obj, key)) keys.push(key);
+  // Ahem, IE < 9.
+  if (_setup.hasEnumBug) _collectNonEnumProps(obj, keys);
+  return keys;
+}
+
+module.exports = keys;