title: ionic2:can't set <ion-content> background color in variables.scss
body: <p>in html:</p>
  
  <pre><code>&lt;ion-content class="bg-style"&gt;
  </code></pre>
  
  <p>in variables.scss:</p>
  
  <pre><code>.bg-style {
      background-color: #f5f0eb;
  }
  </code></pre>
  
  <p>the above codes do not work,but it can work in other tags like <code>&lt;a&gt; &lt;div&gt;</code> and so on,and when I put the style file(.scss,such as test.scss) in the same path as the html file,it can work well also.I do not know if my question is clear,thank you for help.</p>