Hi!

I’d like to propose two minor enhancements:

1.  add a command-line option to check `megatools` version, e.g. `-V` or `--version` or simply `version`;
2.  add `build/` to `.gitignore` as it is IMO the most often used build folder name.

Anyway, thank you very much for your great work!

Tukusej’s Sirs