Fix Python 3 TypeErrors in t2kdm-maid.

[thecuriousneutrino]

Python 3 specific errors in maid.py have been fixed: base64.b64encode expects bytes-like objects as its arguments, which I've satisfied using .encode() methods. Also, the output of base64.b64encode must be a string so that it can be concatenated with ".txt", hence the addition of the .decode() method.