title: Symfony 2 install SonataIntBundle date_time_object not found
body: <p>I want to use SonataIntBundle to translate the twig datetime. </p>
  
  <p>I added in my composer.json: 
      <code>"sonata-project/intl-bundle": "dev-master"</code></p>
  
  <p>AppKernel.php: 
      <code>new Sonata\IntlBundle\SonataIntlBundle(),</code></p>
  
  <p>config:tml:
      <code>sonata_intl:
          timezone:
              default: Europe/Paris
              locales:
                  fr:    Europe/Paris
                  en:    Europe/London</code></p>
  
  <p>I try the code:
     <code>{{ date_time_object | format_datetime(null, 'fr', 'Europe/Paris',constant('IntlDateFormatter::LONG'), constant('IntlDateFormatter::SHORT')) }}
  </code></p>
  
  <p>I get the error: "Variable "date_time_object" does not exist". I missed something ?</p>