def vote(value, voted_by)
      mark = Vote.new(value: value, voted_by_id: voted_by.id, voter_type: voted_by.class.name)
      add_vote_mark(mark)
    end
def vote(value, voted_by)
      mark = Vote.new(value: value, voted_by_id: voted_by.id, voter_type: voted_by.class.name)
      add_vote_mark(mark)
    end
Creates an embedded vote record and updates number of votes and vote value.

 @param [Int,Float] value vote value
 @param [Mongoid::Document] voted_by object from which the vote is done
 @return [Boolean] success flag