Removed some tests, the behaviour should be checked in a test for the YoutubeDL class
The fixed audio files for Youtube have a size lower that the minimum required.
From now on, test_download will run these tests. That means we benefit not only from the networking setup in there, but also from the other tests (for example test_all_urls to find problems with _VALID_URLs).
functionality)
Only works in youtube for the moment.
now all tests working and passing