Repository should use timestamp instead of id for query ordering

[renou]

should be: https://github.com/johnbywater/eventsourcing/blob/26c2b41a5c5bc1c754cdc809bb40e1dce175d144/eventsourcing/infrastructure/stored_event_repos/with_sqlalchemy.py#L137 right now: https://github.com/ApplauseOSS/djangoevents/blob/devel/djangoevents/repository.py#L76

the reason behind is if multiple events get persist to the database, the order of inserts may not be the order of event creation.