title: setState not updating font awesome icon
body: <p>I'm trying to dynamically render font awesome icon in myself written checkbox component. When I'm trying to update state of a  with font awesome icon after clicking on it it is not updating. I've tried to move render to separate function and tried to use react-fontawesome but nothing helps. The state is updating but font awesome icons are the same svg code in html.</p>
  
  <pre><code>...
  state = {
   checked: this.props.checked
  }
  
  toggleCheck = () =&gt; {
    this.setState({ checked: !this.state.checked });  
  };
  
  render () {
  
    const iconUnchecked = 'far fa-square';
    const iconChecked = 'fas fa-check-square';
    const iconClass = this.state.checked ? iconChecked : iconUnchecked;
  
    return (
      &lt;span onClick={this.toggleCheck}&gt;
        &lt;i className={iconClass} /&gt;
      &lt;/span&gt;
    );
  }
  </code></pre>