title: Combine all sass files into a single file
body: <p>Is there any option available in gulp-sass to combine sass files? </p>
  
  <p>For example:</p>
  
  <p><strong>main.scss:</strong></p>
  
  <pre><code>$var: red;
  </code></pre>
  
  <p><strong>control.scss:</strong></p>
  
  <pre><code>@import 'main';
  .a{
    color: $var;
  }
  </code></pre>
  
  <p>The combined output file should be single scss file like below</p>
  
  <pre><code>$var: red;
  .a{
    color: $var;
  }
  </code></pre>