Bug Fix - nginx<->uWSGI interaction

nginx by default buffers data between client and uwsgi app; however
this seems to be causing a problem for large file transfers (>1GB)
as the buffer fills up faster than nginx/client can empty it, at
which point uWSGI terminates with a TIMEOUT message. Turning off
buffering resolves the issue.

Caching may also come into play (not tested without both disabled)
so it's best to disable it as well since we really want nginx to be
serving what deuce serves up, not what it is in its cache.