def to(stop)
      raise InvalidPageStop if stop.nil? || stop.empty?
      raise EventNotFound.new(stop) unless reader.has_event?(stop)
      Specification.new(reader, result.dup { |r| r.stop = stop })
    end
def to(stop)
      raise InvalidPageStop if stop.nil? || stop.empty?
      raise EventNotFound.new(stop) unless reader.has_event?(stop)
      Specification.new(reader, result.dup { |r| r.stop = stop })
    end
Limits the query to events before or after another event.
 {http://railseventstore.org/docs/read/ Find out more}.

 @param start [String] id of event to start reading from.
 @return [Specification]