title: Symfony files which are included in CSS are not found when using assetic
body: <p>I'm using Symfony with Twig and I use assetic. The problem is that my CSS file includes other CSS files like that:</p>
  
  <pre><code>@import url(ie8.css);
  @import url(blocks.css);
  @import url(plugins.css);
  @import url(app.css);
  </code></pre>
  
  <p>And these files are not found when webpage is displayed.
  Same happens with fonts and images. How do I solve this?</p>
  
  <p>I have to mention that I load css files like that:</p>
  
  <pre><code>        {% stylesheets
          '@BaseBundle/Resources/public/plugins/bootstrap/css/bootstrap.min.css'
          '@BaseBundle/Resources/public/css/style.css'
          filter='cssrewrite'
          %}
          &lt;link rel="stylesheet" href="{{ asset_url }}" /&gt;
          {% endstylesheets %}
  </code></pre>