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*).
Yeah, I haven't quite wrapped my head around Ruby yet. Working on it, but I struggle a bit with some parts.

```
onetime --version && echo fish
```

Works outside of Ruby, so that would translate into ``` system "#{bin}/onetime", "onetime --version && echo test" ``` inside of Ruby?