deps: remove usage of arparse

[igor-raits]

That crate didn't have any release for 3 years, would be cool if you would replace it with docopt or clap.

Thanks in advance!

[tailhook]

1. While argparse didn't release too far ago, it works fine.
2. While I don't think argparse is necessary now (I would use structopt nowadays), it's still used in many of my programs, so I have no possibility to remove it everywhere anytime soon.
3. It's only in dev-dependencies, so doesn't influence anything built with the library.

At the end of the day, you can file a PR for replacing it with structopt (I would be reluctant to accept other options, since they don't bring any advantages), I will not allocate any time to do it myself.