title: Vim syntastic scss error, doesn't read the imported files
body: <p>How to make vim syntastic to read the imported files? 
  Currently my scss directory files like this:</p>
  
  <pre><code>scss/
  ----custom.scss
  ----style.scss
  ----variable.scss
  </code></pre>
  
  <p>I import all the scss file into <code>style.scss</code>, so the style.scss contains:</p>
  
  <pre><code>@import 'variable';
  @import 'custom';
  </code></pre>
  
  <p>That's fine, then in my <code>variable.scss</code>, e.g I make a variable of color <code>$primary-color: #3298df;</code>. Then in my <code>custom.scss</code> contains:</p>
  
  <pre><code>a, p {
      color: $primary-color;
      font-weight: bold;
  }
  </code></pre>
  
  <p>The vim syntastic will notify me an error saying that <code>Undefined variable: $primary-color</code>, but if I build the scss file and run in the browser, it works fine. </p>
  
  <p>Any clue for the vim syntastic configuration ?</p>