Fix incorrect id reference when describing linking.
Fix incorrect id reference when describing linking.

An event exposes event_id.

[#656]
arkency/rails_event_store,mpraglowski/rails_event_store,mpraglowski/rails_event_store,mpraglowski/rails_event_store,RailsEventStore/rails_event_store,RailsEventStore/rails_event_store,arkency/rails_event_store,mpraglowski/rails_event_store,RailsEventStore/rails_event_store,RailsEventStore/rails_event_store,arkency/rails_event_store,arkency/rails_event_store