title: How to force SASS to merge external css files?
body: <p>How to force SASS to merge external css files?</p>
  
  <pre><code>//these two files will not merged
  @import "js/font-awesome/css/font-awesome.css";
  @import "js/selectize/css/selectize.css";
  //thess two files will be merged
  @import "js/font-awesome/css/x.scss";
  @import "js/selectize/css/y.scss";
  </code></pre>
  
  <p>I do not want to rename foo.css to foo.sass.</p>