Start using TimeUUID from python-timeuuid library

Summary:
This requires us to merge https://github.com/chronology/python-timeuuid/pull/2 first and create a new release.

The next bottleneck seems like the datastax driver or maybe json.dumps/loads..

Test Plan: -

Reviewers: marcua

Reviewed By: marcua

Differential Revision: https://phabricator.locu.com/D7013