title: Show booleans in Active Admin as 'Yes' and 'No'
body: <p>How can I make active admin to show "Yes" and "No" instead of "true" and "false".</p>
  
  <p>I tried to change in english locale but that doesn't work.
  I'm thinking of monkeypatching boolean classes, but this seems quite ugly.</p>
  
  <p>Is there anything else I can do?</p>