added "rotating" failures list

Just to avoid to surcharge redis with fail jobs.

I had a wrong configuration of my db ip and all my jobs fails causing more than 1 000 000 fails jobs in redis.

The redis server fall because he doesn't have enough ram...

To try the limit just add this line in your initializer/sidekiq : Sidekiq::Failures::Config.max_failures_count = 10_000