Gather all RubyEventStore under Error class
Gather all RubyEventStore under Error class

It might be convenient to be able to catch all RES errors by rescuing
only RubyEventStore::Error instead of getting acknowledged with all
present and future errors.

[#620]

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