add example code to get_shared_playlist_contents [closes #187]
add example code to get_shared_playlist_contents [closes #187]

dvirtz/gmusicapi,simon-weber/Unofficial-Google-Music-API,tanhaiwang/gmusicapi,thebigmunch/gmusicapi,simon-weber/gmusicapi,TheOpenDevProject/gmusicapi,dvirtz/gmusicapi,peetahzee/Unofficial-Google-Music-API