code: function BartererServer(options) {
    options = options || {};
    var specifiedHttpPort = options.httpPort || HTTP_PORT;
    var httpPort = process.env.PORT || specifiedHttpPort;
  
    var app = express();
  
    var instance = new Barterer(options);
    options.app = app;
    instance.configureRoutes(options);
  
    app.listen(httpPort, function() {
      console.log('barterer is listening on port', httpPort);
    });
  
    return instance;
  }
docs: BartererServer Class
  Server for barterer, returns an instance of barterer with its own Express
  server listening on the given port.
  @param {Object} options The options as a JSON object.
  @constructor