Introduce One Time Passwords

[marcofeltmann]

Since I'm unable to find out how you structured that document, I'd like to feature-request the One Time Password capabilities of Gopass.

Both HOTP and TOTP are supported with TOTP being the more convenient one.
Information is in the documentation at https://github.com/gopasspw/gopass/blob/master/docs/features.md#adding-otp-secrets

[woile]

Hey which commands would you like to add? You can make a PR modifying only the markdown file. This is an old project of mine with poor docs, sorry for that. In case you wanna give it a hand again, I've updated the README and the Makefile, so I think it should work now.