code: function (name, version) {
      if (!name || !_.isString(name)) {
        throw new Error('Please pass in a command name!');
      }
  
      for (var a in this.aggregates) {
        var aggr = this.aggregates[a];
        var cmd = aggr.getCommand(name, version);
        if (cmd) {
          return aggr;
        }
      }
  
      for (var a in this.aggregates) {
        var aggr = this.aggregates[a];
        var cmdHndl = aggr.getCommandHandler(name, version);
        if (cmdHndl && cmdHndl !== aggr.defaultCommandHandler) {
          return aggr;
        }
      }
  
      debug('no matching aggregate found for command ' + name);
  
      return null;
    }
docs: Return the aggregate that handles the requested command.
  @param {String} name    command name
  @param {Number} version command version
  @returns {Aggregate}