title: upgrade ICU and intl
body: <p>After installing Symfony 2 and check /config.php I got this notification:</p>
  
  <p>intl ICU version installed on your system is outdated (55.1) and does not match the ICU data bundled with Symfony (57.1)
  To get the latest internationalization data upgrade the ICU system package and the intl PHP extension.</p>
  
  <p>How can I upgrade this?
  I'm using Ubuntu 16.04</p>