app.yaml: remove expiration headers.
app.yaml: remove expiration headers.

The default for appengine sounds about right: 10 minutes for prod server,
and no cache for dev server.  That makes testing work better.  Otherwise
Chrome annoyingly caches render.js even if you shift-reload the page.

apenwarr/afterquery,apenwarr/afterquery,apenwarr/afterquery,apenwarr/afterquery,apenwarr/afterquery