add data to locals, if there is a `data` entry point in `.pennyrc`

[lunelson]

1. must use pennyrc.js format
2. data key there would either contain a Promise, or require a file whose module.exports is a Promise
3. that Promise would resolve the data i.e. dataPromise.then((data) => {/*...*/})
4. This data would be attached to pugLocals under the key data