Allow nlbcli to also be used as a Python module (library)

[Tunas1337]

Having a CLI tool to access my bank account is amazing, and I salute you for thinking to do what many of us have always wanted to, yet none of us have had the courage to do.
However, I can think of many use cases for a Python library that does the same task, for integration in more complex tools without relying on calling "nlbcli" in shell scripts (or, in Python, os.system) and using regex and slicing (for example, echo -e Имаш уште само $(nlbcli accounts balance | grep "Available balance:" | tail -c +20 | head -c -8) денари,\\nсмири се со трошењето can be done much more elegantly with a Python library, not to mention it can be more functional.)

Please let me know what you think.

[whoeverest]

Agreed! This being a library and a CLI has been on my mind since the start, but in true MVP fashion I wanted to release it sooner and receive feedback. :)

Do you have any experience with python packaging / modules / making Python act sane both in CLI mode and as a library? Any advice? If you want to do a PR let me know. I'll eventually do this myself, but help is always appreciated.