promptListInteractive swallows Control-C
If you run the following nim program:

```nim
import nimblepkg/cli
discard promptList(dontForcePrompt, "Choose something?", ["a", "b", "c"])
```

And press Control-C, it will *not* break out of the prompt, but I expect that it *should* stop the program.

I'm on macOS.

```
nimble v0.9.0 compiled at 2018-10-19 22:47:19
git hash: 22aa3c1d1392d7878d039250ecf0ffeadf3ba0cc
```