Support for python 3 in python example

[Delanii]

Hello, I have encountered a small issue while trying out you FFI example when running python variant with python 3. It requires to declare a specific encoding in string output (rows 38 and 72 in demo.py). It is only a small issue, I just wanted to point it out if you would be interrested to adress that. Thank you for great solution, I am learning FFI with Go and this is a great piece of code to learn from. Regards