title: Date regex replacement
body: <p>I've learn a lot about regex but here I'm blocking.</p>
  
  <p>There is some strings :</p>
  
  <pre>
  6 September 2013
  13 Mars 2014
  20 Mars 2012
  </pre>
  
  <p>I need to transform the first one into : 06 September 2013</p>
  
  <p>Thanks for your help</p>