Fix the decompress -d argument description

[hivehand]

This corrects the description of said argument. (Feel free to discard my phrasing and replace it with your own. I'm just submitting mine to spare you possible work.)

Fixes #264.

[marcospb19]

I'll just make one commit on your branch because the flag you're referring is -d --dir and not -o --dir, we fixed this typo in the main branch already but the version you downloaded still has it in.

Thanks!