title: Why don't we have col-xs-offset-* classes in Bootstrap-3?
body: <p>I read in <a href="http://getbootstrap.com/css/#grid-offsetting" rel="nofollow">twitter bootstrap-3 docs</a> that it doesn't support <code>col-xs-offset-*</code> classes. This doesn't seem in line with mobile first. Is there a good reason for it? I thought they could be useful.  </p>
  
  <p>I read <a href="https://github.com/twbs/bootstrap/issues/9597" rel="nofollow">this issue report</a> on github but couldn't find any sutitable justification.</p>