add use statement for DocumentManager. fix #634

Author: dbu

quick_tour/the_model.rst

@@ -98,11 +98,11 @@ by creating a new class in the AcmeMainBundle::
     {
         public function getOrder()
         {
-            // refers to the order in which the class' load function is called 
+            // refers to the order in which the class' load function is called
             // (lower return values are called first)
             return 10;
         }
-    
+
         public function load(ObjectManager $documentManager)
         {
         }
@@ -111,6 +111,7 @@ by creating a new class in the AcmeMainBundle::
 The ``$documentManager`` is the object which will persist the document to
 PHPCR. But first, you have to create a new Page document::
 
+    use Doctrine\ODM\PHPCR\DocumentManager;
     use Symfony\Cmf\Bundle\SimpleCmsBundle\Doctrine\Phpcr\Page;
 
     // ...