Shouldn't it be updated to react-transition-group?

This video should really be redo. The changes made to the library do make it slightly more complicated to follow along using the old libraries.

PS: Yes I know you can simply use the old "drop-in" library, but it would be nice for this video to be updated.

Some import details to help people trying to do this on this video.

Step 1: change the import to

import { CSSTransition, TransitionGroup } from 'react-transition-group';

Step 2: Replace the ul tag with the follow. We will add CSSTransition in the next step.

<TransitionGroup component="ul">
  {guests} 
</TransitionGroup>

Step 3: Adding CSSTransition. In this step you will find the code that generates our guests. In the map function wrap the li tags with a CSSTransition as in my example below

<CSSTransition component="li" key={name.name}
timeout={500}
classNames="slide">
  <li>
    {name.name}
    <button onClick={this.handleRemove.bind(this, index)}>Remove</button>
  </li>
</CSSTransition>

To make this new addon as compatible with the videos, use the 1.x versions. They're designed to be a "drop-in" replacement. I used them and only had to change the imports slightly.

More info can be found at https://github.com/reactjs/react-transition-group/tree/v1-stable