Implemented retention processing
Merge branch 'master' of git://github.com/rackspace-titan/qonos into retention
Merge branch 'master' of git://github.com/rackspace-titan/qonos into retention

Conflicts:
	qonos/tests/unit/worker/snapshot/test_snapshot.py
	qonos/worker/snapshot/snapshot.py
Various bug fixes to worker
Merge branch 'master' of git://github.com/rackspace-titan/qonos into retention
Merge branch 'master' of git://github.com/rackspace-titan/qonos into retention
Fixed some test that broke after merge.
Fixed some final bugs. Retention actually works now.
Merge pull request #73 from esheffield/retention

Retention implementation