workaround for mopidy/mopidy#62 - appends folder names to playlist
- use path separators instead of square brackets
- use generator expression instead of list comprehension
- fix bug for empty but not None list of folders
spotify folders not necessary as a positional arg
- rename to folders
- remove confusing None for starred playlists
Merge pull request #479 from alzeih/develop

Prepend name of Spotify playlist folders to playlist name (fix #62)