old_contents: import React from 'react';
  import {default as KataGroupsData} from '../katagroups.js';
  
  export default class KataGroupsComponent extends React.Component {
  
    static propTypes = {
      kataGroups: React.PropTypes.instanceOf(KataGroupsData).isRequired
    };
  
    render() {
      const {kataGroups} = this.props;
      return (
        <div id="nav" className="pure-u">
          <a href="#" className="nav-menu-button">Menu</a>
  
          <div className="nav-inner">
            <div className="pure-menu">
              <ul className="pure-menu-list">
                <li className="pure-menu-heading">Kata groups</li>
                <li className="pure-menu-item">
                </li>
                {kataGroups.groups.map(kataGroup => <li className="pure-menu-item">
                  <a href={`#kataGroup=${encodeURIComponent(kataGroup.name)}`} className="pure-menu-link">{kataGroup.name} <span className="email-count">({kataGroup.katasCount})</span></a>
                </li>)}
              </ul>
            </div>
          </div>
        </div>
      );
    }
  }
  
  
new_contents: import React from 'react';
  import {default as KataGroupsData} from '../katagroups.js';
  
  export default class KataGroupsComponent extends React.Component {
  
    static propTypes = {
      kataGroups: React.PropTypes.instanceOf(KataGroupsData).isRequired
    };
  
    render() {
      const {kataGroups} = this.props;
      return (
        <div id="nav" className="pure-u">
          <a href="#" className="nav-menu-button">Menu</a>
  
          <div className="nav-inner">
            <div className="pure-menu">
              <ul className="pure-menu-list">
                <li className="pure-menu-heading">Kata groups</li>
                <li className="pure-menu-item">
                </li>
                {kataGroups.groups.map(kataGroup => <li className="pure-menu-item">
                  <a href={kataGroup.url} className="pure-menu-link">{kataGroup.name} <span className="email-count">({kataGroup.katasCount})</span></a>
                </li>)}
              </ul>
            </div>
          </div>
        </div>
      );
    }
  }
  
  
subject: Use the new `url` property.