new formula: onetime

New formula: onetime. Assists users in creating one-time pads. Still actively supported upstream, and has gathered a lot of renewed interest thanks to Hak5 covering the tool recently.

(*This is my first formula created entirely from scratch, and I'm pretty thrilled to have actually managed to make it work around Homebrew's syntax & formula requirements. Extremely thoroughly tested, so hopefully will pass the build bot first time*).
I can't seem to get it to take to any test, even a simple one, and yet the formula works if I test separately (ie, by calling ``` onetime ``` from the CLI).

Am I doing something wrong?

  test do
  system "#{bin}/onetime", "--help"
  end
end
```