Initial role implementation

Why have both this and the `npi` wrapper?  Might be clearer to have this line be:

```bash
node {{ npi_prefix }}/npi.js start {{ item.key }} --foreground
```

This offers the advantage of having the full path to the `npi.js` file in the upstart config, which will make it easier to debug.  Also removes the need for the `npi` file