Update for Python 3 and IDA 7.4+

Hey,
Thanks for your work,
Just so you know, I tried to port to Python 3 and IDA 7.4+ here: https://github.com/securechicken/ida-bpf-processor-74/tree/update-p3-ida74
Worked fine for me on 7.7.
Tell me if you need a PR, otherwise feel free to get what you need from it to update!

Regards.