title: Iterate on symfony2 translation element childs
body: <p>I am using symfony2 translation tool with yml files types.</p>
  
  <p>I have something like that :</p>
  
  <pre><code>carousel:
      slide1:
          title: At nunc si ad aliquem bene
          text: Altera sententia est quae
      slide2:
          title: Vita est illis semper in fuga
          text: Haec igitur lex in amicitia
      slide3:
          title: Cum haec taliaque sollicitas
          text: Tandem id ut optimum factu
  </code></pre>
  
  <p>Is it possible to iterate on "carousel" childs in twig with symfony? </p>
  
  <p>Something like :</p>
  
  <pre><code>{% for slide in carousel|trans %}
      {{ slide.title }}
      {{ slide.text }}
  {% endfor %}
  </code></pre>