title: Flex-direction column makes flex items overlap IE11
body: <p>I'm running into an issue using flexbox in IE11. When using <code>flex-direction: column</code> the flex-items overlap:</p>
  <p><a href="https://i.stack.imgur.com/fHBw0.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/fHBw0.png" alt="enter image description here" /></a></p>
  <p>In other browsers (chrome, safari) it looks like this:</p>
  <p><a href="https://i.stack.imgur.com/c2h7P.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/c2h7P.png" alt="enter image description here" /></a></p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="false" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>.container {
    display: flex; 
    flex-direction: column;
  }
  .flex {
    flex: 1 1 0%;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="container"&gt;
    &lt;div class="flex"&gt;
      Hello
    &lt;/div&gt;
    &lt;div class="flex"&gt;
      World
    &lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  <p>I've made a codepen to demonstrate the issue:</p>
  <p><a href="http://codepen.io/csteur/pen/XMgpad" rel="nofollow noreferrer">http://codepen.io/csteur/pen/XMgpad</a></p>
  <p>What am I missing to make this layout not overlap in IE11?</p>