title: SASS/Flexbox not working
body: <p>I'm trying to apply a flexbox layout to my elements based on <a href="https://www.predix-ui.com/#/css/layout/px-flexbox-design" rel="nofollow noreferrer">this</a> example. In the .html I have:</p>
  
  <pre><code>&lt;link rel="import" href="seed-app-styles.html"&gt;
  ...
  &lt;template is="dom-if" if="{{isEqual(selected,'pacing')}}" restamp&gt;
      &lt;div class="px-login" id="pacing" class="flex flex--col flex--center flex--middle"&gt;
            &lt;div&gt;1&lt;/div&gt;
            &lt;div&gt;2&lt;/div&gt;
            &lt;div&gt;3&lt;/div&gt;
      &lt;/div&gt;        
  &lt;/template&gt;
  </code></pre>
  
  <p>And I do have flex enabled in the .scss file:</p>
  
  <pre><code>@import "px-flexbox-design/_base.flexbox.scss";
  </code></pre>
  
  <p>However, I'm still not getting a flexbox:</p>
  
  <p><a href="https://i.stack.imgur.com/TdDC1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/TdDC1.png" alt="enter image description here"></a></p>
  
  <p>And the classes do get generated into the seed-app-styles.html:</p>
  
  <pre><code>.flex {
    display: -ms-flexbox;
    display: flex; }
  
  .inline--flex {
    display: -ms-inline-flexbox;
    display: inline-flex; }
  
  .flex--row {
    -ms-flex-direction: row;
        flex-direction: row; }
  </code></pre>
  
  <p>I would expect the div to be centered. What am I missing here?</p>
  
  <p>There is no .css file - a .html is generated when I run gulp, that's the one being imported.</p>
  
  <p>The template is used in the index.html:</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
  &lt;head&gt;
  
  ...
    &lt;meta name="viewport" content="width=device-width, initial-scale=1.0"&gt;
  
    &lt;link
      id="main-element-import"
      rel="import"
      href="/elements/seed-app/seed-app.html"
      async&gt;
  
  &lt;/head&gt;
  &lt;body class="loading"&gt;        
    &lt;seed-app&gt;&lt;/seed-app&gt;
  
    &lt;script src="/elements/dev-guide/dev-guide-bootstrap.js"&gt;&lt;/script&gt;
  
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>