fixed AutoTimestamp example in advanced app

fixes yiisoft#429

Author: cebe

apps/advanced/common/models/User.php

@@ -37,8 +37,7 @@ public function behaviors()
 			'timestamp' => array(
 				'class' => 'yii\behaviors\AutoTimestamp',
 				'attributes' => array(
-					ActiveRecord::EVENT_BEFORE_INSERT => 'create_time',
-					ActiveRecord::EVENT_BEFORE_INSERT => 'update_time',
+					ActiveRecord::EVENT_BEFORE_INSERT => array('create_time', 'update_time'),
 					ActiveRecord::EVENT_BEFORE_UPDATE => 'update_time',
 				),
 			),