code: function (changed, previous, events, command, callback) {
      async.eachSeries(this.getBusinessRules(), function (rule, callback) {
        rule.check(changed, previous, events, command, callback);
      }, callback);
    }
docs: Checks business rules.
  @param {Object}   changed  The new aggregate values.
  @param {Object}   previous The previous aggregate values.
  @param {Array}    events   All new generated events.
  @param {Object}   command  The command that was handled.
  @param {Function} callback The function, that will be called when this action is completed.
  `function(err){}`