session: Rename playlist{_container => s}
session: Rename published_{container => playlists}_for_user()
plcont: Add __len__()
playlist: Add PlaylistType enum
travis: Run flake8 as part of build
playlist: Add folder classes
utils: Make get_with_growing_buffer() work for more functions
plcont: Add __getitem__()
plcont: Make repr() look like a list