navigate(name, argument) {
    if (typeof this.routes[name] === 'function') {
      return this.routes[name].call(null, this, argument).then(() => this);
    }

    throw new Error(`No routes called: ${name}`);
  }
Navigate to a route
@param  {String} name Route name
@param  {*}      arg  A single argument to pass to the route handler
@return  {Promise} Promise this.