title: bootstrap 3 border-radius less mixin gone
body: <p>Bootstrap's <code>.border-radius()</code> mixin is <a href="https://github.com/twbs/bootstrap/blob/master/less/mixins.less#L102" rel="noreferrer">no longer there</a> in version 3. </p>
  
  <p>I am working on converting my codebase and thought of this omission as rather strange. Has <code>.border-radius</code> been replaced by some other mixin? Is its use discouraged, and if so why? </p>