support python 3

[infinity0]

Hi, 2to3 runs cleanly on current pysodium - please apply it! Thanks!

[stef]

chalonga maintains a python3 compatible version:
https://github.com/chalonga/pysodium3

i have no interest in supporting academic niche languages >:)

[stef]

if you look at the history you can see i tried. but the effort was worth to remove /o\