clarify addition of mobileclient
clarify addition of mobileclient

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