Improved option '--srt-lang'
- it shows the argument in case of missing subtitles
- added language suffix for non-english languages (e.g. video.it.srt)
* ask for a --verbose log when reporting bugs in README.md
* re-enable Escapist test, seems stable now
* check that we are not downloading multiple videos when the template is fixed (NOT a complete fix: not detecting playlists)