title: Map Subdomain to specific AppEngine app version
body: <p>I have a Python app at www.example.com. I want to create a subdomain that will map to a different version of my app (actually a Java app). So want I want to do is:
  www.example.com -> example.appspot.com [0]
  subdomain.example.com -> subdomain.example.appspot.com [?]</p>
  
  <p>Is it doable??</p>