title: Animate React component when unmount/leave
body: <p>I want to use Velocity to fade out a component when the component leaves . I'm calling the callback but there is no animation. What is wrong with the code below?</p>
  
  <pre>
  export class Foo extends Component {
  
        componentWillEnter(cb) {
          cb();
        }
  
        componentWillLeave(cb) {
           const node = findDOMNode(el);
           Velocity(node, { opacity: 0 }, { duration:200 });
           cb();
        }
  }
  </pre>