fix less.mode in node

Author: cloudhead

lib/less/parser.js

@@ -10,7 +10,7 @@ if (typeof environment === "object" && ({}).toString.call(environment) === "[obj
     // Node.js
     less = exports,
     tree = require('./tree');
-    less.mode = 'rhino';
+    less.mode = 'node';
 } else {
     // Browser
     if (typeof(window.less) === 'undefined') { window.less = {} }