Fixed some of the comments

Author: wouterj

book/testing.rst

@@ -54,7 +54,7 @@ unit tests. Suppose, for example, that you have an *incredibly* simple class
 called ``Calculator`` in the ``Util/`` directory of the app bundle::
 
     // src/AppBundle/Util/Calculator.php
-    namespace AppBundle\Utility;
+    namespace AppBundle\Util;
 
     class Calculator
     {

book/validation.rst

@@ -539,7 +539,7 @@ class to have at least 3 characters.
         {
             /**
              * @Assert\NotBlank()
-             * @Assert\Length(min="3")
+             * @Assert\Length(min=3)
              */
             private $firstName;
         }
@@ -823,7 +823,7 @@ user registers and when a user updates their contact information later:
                     'groups' => array('registration'),
                 )));
 
-                $metadata->addPropertyConstraint('city', Assert\Length(array(
+                $metadata->addPropertyConstraint('city', new Assert\Length(array(
                     "min" => 3,
                 )));
             }