Allow unambiguous shortened long-options about argparse

[densestvoid]

Python argparse confirmed, according to https://docs.python.org/3/library/argparse.html, allow_abbrev is a parameter for ArgumentParser object.

[akamensky]

I don't think that is necessary. This adds ambiguity to the options as well as adds on complexity of parsing.

This library is inspired by argparse, it does not intent on copying it 100% (which would not be possible anyway because of strict typing).