* Allow URLs that have a 'subdirectory' before the actual program name, e.g.
  'xyz/xyz-episode-1'.
* The author and broadcastDate fields in the XML file may be empty.
* Add test case for the two problems above.

All the code uses now the urlopen method of YoutubeDL

Use the timeout argument of the `OpenerDirector.open` method instead

The date is now interpreted as UTC for consistency.