title: HTTP GET request responses very slow when add Header "Range"
body: <p>When add header <code>Range</code> to request, the speed is about 3KB/s.
  Without <code>Range</code>, the speed is about 200KB/s.
  Anybody know why?</p>
  
  <pre><code>GET /assets/svn-book.pdf HTTP/1.1
  Range: bytes=0-1945365
  Host: sethfeng.github.io
  Connection: close
  User-Agent: Paw/2.3.2 (Macintosh; OS X/10.11.3) GCDHTTPRequest
  </code></pre>