prompt missing after a recent npm update

The prompt is missing after invoking those commands, both in bash & zsh:

```
$ npm -g i david@7.0.2
$ david
```

This is happening on OS X 10.11.5 in Terminal.app.

This is related to the new progress bar in npm 3.10.x. If I revert the internal david npm copy to the latest 3.9, it works fine. With npm 3.10 internally the only way to get the prompt back is to invoke some npm command that shows the new progress bar like `npm install`.

I'd report an issue to npm but npm itself cleans up after its own commands just fine... So I'm not sure if it's an npm issue or is david interacting with it in a weird way.