title: React PropTypes in Meteor doesn't work for me
body: <p>I tried different meteor/react tutorials and I always have the same problem.</p>
  
  <p>I don't know why PropTypes don't display warnings in console if something is wrong. For example:</p>
  
  <p>If I remove title <code>&lt;TitleBar title="Test title"/&gt;</code> The code still works normal without warnings even if it's required.</p>
  
  <p>If I change string in object, bool or array <code>title: PropTypes.string.isRequired</code> everything still works normal without warnings.</p>
  
  <pre><code>import React from 'react';
  import PropTypes from 'prop-types';
  
  export default class TitleBar extends React.Component {
    render(){
      return (
        &lt;div&gt;
          &lt;h1&gt;{this.props.title}&lt;/h1&gt;
        &lt;/div&gt;
      );
    }
  }
  
  TitleBar.propTypes = {
    title: PropTypes.string.isRequired
  };
  </code></pre>
  
  <p>I also tried official Meteor/React tutorial and I got the same problem.
  <a href="https://www.meteor.com/tutorials/react/components" rel="nofollow noreferrer">https://www.meteor.com/tutorials/react/components</a></p>
  
  <p>Is PropTypes just for testing purpose?</p>