Revert "Revert "Mutant now requires Ruby 2.5""
Revert "Revert "Mutant now requires Ruby 2.5""

This reverts commit eb3de83d847a124d68cc644d32e9197e04dcae82.

RailsEventStore/rails_event_store,arkency/rails_event_store,RailsEventStore/rails_event_store,mpraglowski/rails_event_store,RailsEventStore/rails_event_store,mpraglowski/rails_event_store,arkency/rails_event_store,RailsEventStore/rails_event_store,arkency/rails_event_store,mpraglowski/rails_event_store,arkency/rails_event_store,mpraglowski/rails_event_store