Move Video class to a separate library

+ improve error handling
+ youtube-dl update

README.md

@@ -148,32 +148,8 @@ so that it points to your ffmpeg/avconv binary (`/usr/bin/avconv` on Debian/Ubun
 
 ## Use as library
 
-AllTube can also be used as a library to extract a video URL from a webpage.
-
-You can install it with:
-
-```bash
-composer require rudloff/alltube
-```
-
-You can then use it in your PHP code:
-
-```php
-use Alltube\Config;
-use Alltube\Video;
-
-require_once __DIR__.'/vendor/autoload.php';
-
-Config::setOptions(
-    [
-        'youtubedl' => '/usr/local/bin/youtube-dl',
-    ]
-);
-$video = new Video('https://www.youtube.com/watch?v=dQw4w9WgXcQ');
-$video->getUrl();
-```
-
-You can also have a look at this [example project](https://github.com/Rudloff/alltube-example-project).
+The `Video` class is now available as [a separate package](https://packagist.org/packages/rudloff/alltube-library)
+so that you can reuse it in your projects.
 
 ## JSON API