Get rid of Redis namespaces

Everyone can contribute. Help move this issue forward while earning points, leveling up and collecting rewards.

• Close this issue

It's not the best practice anymore. See http://www.mikeperham.com/2015/09/24/storing-data-with-redis/ and https://github.com/mperham/sidekiq/issues/2586

We can use different Redis databases instead because Redis namespaces is a hack.

/cc @DouweM @smcgivern @stanhu