title: Merge overlapping time intervals, how?
body: <p>Anyone could help me in a query that **merge a interval of datas? <br>
  ex: Common select: </p>
  
  <blockquote>
    <p>SELECT id, date_start, date_end FROM evento ORDER BY date_start</p>
  </blockquote>
  
  <p>I GOT THIS:<br> 
  <img src="https://i.stack.imgur.com/52jtS.jpg" alt="pgsql result">
  <br>
  <br>
  FROM THIS:<br>
  <img src="https://i.stack.imgur.com/xM8A2.jpg" alt="web agenda">
  <br>
  <br>
  but a want a query that return this:<br></p>
  
  <blockquote>
    <p>01 - 2013-10-11 08:00:00  2013-10-11 15:00:00<br> 02 - 2013-10-11
    16:00:00  2013-10-11 19:00:00</p>
  </blockquote>
  
  <p>Thanks a lot!</p>