code: function Update(subject, source) {
      if (!(this instanceof Update)) {
          return new Update(subject, source);
      }
      this.id = uuid.v4();
      this.timestamp = Date.now();
  
      // Populate subject
      subject = subject || {};
      this.address = subject.address;
      this.incarnationNumber = subject.incarnationNumber;
      this.status = subject.status;
  
      // Populate source
      source = source || {};
      this.source = source.address;
      this.sourceIncarnationNumber = source.incarnationNumber;
  }
docs: Create a new Update
  @param {IMember} subject the subject of the update.
  @param {IMember} [source] the source of the update.
  @constructor