sys: Mark as deprecated

PR-URL: https://github.com/iojs/io.js/pull/317
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

discussed at TC meeting, deprecate, don't remove

lib/sys.js

@@ -1,5 +1,13 @@
 'use strict';
 
+var util = require('util');
+
 // the sys module was renamed to 'util'.
 // this shim remains to keep old programs working.
-module.exports = require('util');
+// sys is deprecated and shouldn't be used
+
+var setExports = util.deprecate(function() {
+  module.exports = util;
+}, 'sys is deprecated. Use util instead.');
+
+setExports();