fixed CS

doc/providers/serializer.rst

@@ -72,10 +72,10 @@ The ``SerializerServiceProvider`` provider provides a ``serializer`` service::
     })->assert("_format", "xml|json")
       ->assert("id", "\d+");
       
-Use a Cache
------
+Using a Cache
+-------------
 
-To use a cache you can register it in the specified encoder needed. All you need to do is have a class implementing ``Doctrine\Common\Cache\Cache``::
+To use a cache, register a class implementing ``Doctrine\Common\Cache\Cache``::
 
     $app->register(new Silex\Provider\SerializerServiceProvider());
     $app['serializer.normalizers'] = function () use ($app) {
@@ -83,4 +83,3 @@ To use a cache you can register it in the specified encoder needed. All you need
             new \Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer(new ClassMetadataFactory(new  AnnotationLoader(new AnnotationReader()), $app['my_custom_cache']))
         ];
     };
-