title: 'Gatsby develop' support for IE11
body: <p>Say I wanted to support IE11 (and sadly, I do), how would I go about making <code>gatsby develop</code> work on that poor old browser?</p>
  
  <p>Right now, I get this message:</p>
  
  <pre><code>webpack-hot-middleware's client requires EventSource to work.
  </code></pre>
  
  <p>This <a href="https://github.com/Yaffle/EventSource" rel="nofollow noreferrer">polyfill looks promising</a>, but that's as far as I've made it. </p>
  
  <p>Any help?</p>
  
  <p>P.S. Probably worth mentioning that I'm using Gatsby v 2.4.7</p>