title: Symfony2: HTML inside translation message
body: <p>In <code>messages.en.yml</code>, I have </p>
  
  <pre><code>confirmed: Congrats %username%, your account is now activated.
  </code></pre>
  
  <p>But I want to 'bold' username to example ... how can I made this ?</p>
  
  <pre><code>confirmed: Congrats &lt;span class='bold'&gt;%username%&lt;/span&gt;, your account is now activated.   
  </code></pre>
  
  <p>Of course I could use two sentence in this example like</p>
  
  <pre><code>first: Congrats
  second: , your account ... 
  </code></pre>
  
  <p>and inside twig use the html tag but this seems very dirty.</p>