BasE91 encoding & decoding

好久没更新了啊，我才不会说是因为我忘了密码又懒得重置，然后又犯了拖延症，抽空找回继续刷

BasE91（http://base91.sourceforge.net/） is a method for encoding binary as ASCII characters. It is more efficient than Base64 and needs 91 characters to represent the encoded data.

The following ASCII charakters are used:

'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'
'!#$%&()*+,./:;<=>?@[]^_`{|}~"'

Create two functions that encode strings to basE91 string and decodes the other way round.

b91encode('test') = 'fPNKd'
b91decode('fPNKd') = 'test'

b91decode('>OwJh>Io0Tv!8PE') = 'Hello World!'
b91encode('Hello World!') = '>OwJh>Io0Tv!8PE'

简述：就是实现一个basS91的编码和解析，暂时没解决，顺便贴一个base64的参考 

https://blog.youkuaiyun.com/qq_20545367/article/details/79538530 

@艾华生https://my.youkuaiyun.com/qq_20545367