Spew nginx stats too

Summary: We're sending *much* fewer bytes than php-ng. Turns out this is because we gzip-compress everything by default.

Confirmed with:

  curl http://devbig076.prn2.facebook.com:8090/ | wc -c # gets me the same number of bytes as php-ng
  curl -H 'Accept-Encoding: gzip' http://devbig076.prn2.facebook.com:8090/ | wc -c # gets me the lower number

Reviewed By: @ptarjan

Differential Revision: D1552801