Added test for metadata content and generate_id uniqueness
Added test for metadata content and generate_id uniqueness

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