upgraded gunicorn, removed deprecated flag, and added timezone to logging

Upgrade of gunicorn brings it to a version that includes timezone in access log. As far as I can tell it's working - there appear to be two bugs in running the nose tests that also exist in 0.7.3, unless I'm running it wrong.
Removing useless stuff indeed seems like an acceptable reason (note that in v0.18, --debug or its absence had strange side-effects on logging IIRC) - but since we are moving up, I'm happy :-)