public function getAuthenticationUrl($state = null, $forceVerify = false)
    {
        return 'https://api.twitch.tv/kraken/oauth2/authorize?response_type=code'
        .'&client_id='.config('twitch-api.client_id')
        .'&redirect_uri='.config('twitch-api.redirect_url')
        .'&scope='.implode(config('twitch-api.scopes'), '+')
        .'&state='.$state
        .'&force_verify='.($forceVerify ? 'true' : 'false');
    }