title: App Engine - How to set "Vary: Accept-Encoding" header for static files
body: <p>Google Page Speed says.</p>
  
  <blockquote>
    <p>The following publicly cacheable, compressible resources should have a "Vary: Accept-Encoding" header:</p>
  </blockquote>
  
  <p>for my css and js files.</p>
  
  <p>How can I set google app engine to do this?</p>