fixed some references in the docs

doc/cookbook/session_storage.rst

 How to use PdoSessionStorage to store sessions in the database
 ==============================================================
 
-By default, the :doc:`SessionServiceProvider <providers/session>` writes
+By default, the :doc:`SessionServiceProvider </providers/session>` writes
 session information in files using Symfony2 NativeFileSessionStorage. Most
 medium to large websites use a database to store sessions instead of files,
 because databases are easier to use and scale in a multi-webserver

doc/providers/translation.rst

@@ -157,9 +157,9 @@ Once loaded, the translation service provider is available from within Twig temp
 
     {{ app.translator.trans('translation_key') }}
 
-Even better: register the :doc:`SymfonyBridgesServiceProvider <providers/symfony_bridges>` and you will get
-the TranslationExtension of the bridge allowing you to translate strings in
-the Twig way:
+Even better: register the :doc:`SymfonyBridgesServiceProvider
+</providers/symfony_bridges>` and you will get the TranslationExtension of the
+bridge allowing you to translate strings in the Twig way:
 
 .. code-block:: jinja
 

doc/providers/twig.rst

@@ -28,8 +28,8 @@ Services
 * **twig**: The ``Twig_Environment`` instance. The main way of
   interacting with Twig.
 
-* **twig.configure**: :doc:`Protected closure <services#protected-closures>` that takes the Twig
-  environment as an argument. You can use it to add more
+* **twig.configure**: :doc:`Protected closure </services#protected-closures>`
+  that takes the Twig environment as an argument. You can use it to add more
   custom globals.
 
 * **twig.loader**: The loader for Twig templates which uses