private function registerParsers()
    {
        $this->singleton(Contracts\Parsers\RefererParser::class, function () {
            return new Parsers\RefererParser(
                new \Snowplow\RefererParser\Parser
            );
        });

        $this->singleton(Contracts\Parsers\UserAgentParser::class, function (AppContract $app) {
            return new Parsers\UserAgentParser(
                \UAParser\Parser::create(), $app->make('path.base')
            );
        });
    }