bump sidekiq
downgrade multi_json
Revert "downgrade multi_json"

This reverts commit 4c4a98f42e455c53018251584ec8dbf6b15792b1.
Do not pass AR objects to Sidekiq

In the new version Sidekiq calls JSON.generate on the passed arguments, which blows up with AR objects
Merge branch 'develop' into social.mrzyx.de