replace hermann gem with ruby-kafka or otherwise

[codefromthecrypt]

https://github.com/reiseburo/hermann has been dead for over 2 years and requires jruby
https://github.com/zendesk/ruby-kafka looks very active

[codefromthecrypt]

actually it seems wrong.. while hermann is dead activity wise, it doesn't seem to require jruby https://github.com/reiseburo/hermann#mri-only