Rails 6 support released as clone

[priit]

First thank you for all authors for greate work!

I needed Rails 6 support and created a new clone and released it at https://github.com/gitlabeu/userstamper

And as a gem:

gem install userstamper

Main changes: Rails 6 support and code cleanup Renamed to userstamper deleted_by is not supported because soft-delete is not recommended

Enjoy!