zlib codec has been removed in python3.
Merge
Failed previous merge.
Merge remote-tracking branch 'origin/master' into p3k

Conflicts:
	raven/transport/base.py
	raven/transport/threaded.py
	raven/utils/__init__.py
	raven/utils/serializer/base.py
	raven/utils/serializer/manager.py
	raven/utils/urlparse.py
	raven/utils/wsgi.py