add tags to .gitignore
change conf dir to .netease-musicbox
add Constant
add number key shortcuts
number shortcuts: remember last position when nav up
add api for fetch playlist classes
impl: 精选歌单 > 全站置顶
impl: get playlist classes
impl: play songs under playlist classes
add requirement BeautifulSoup4
bug fix: user list error
Merge pull request #1 from hbprotoss/master

添加主页下，全部歌曲-歌单，按歌单分类选择来听的功能，增加数字快捷键功能