Async functions

[groenroos]

The get function needs to use Promises in order to fetch data from the database, but Pug doesn't seem to support async/await functions out-of-the-box.

Fix it so that the get function can output async data into the template.

[groenroos]

Without having tested anything, there is a pug-async (which seems to be unmaintained). It's not clear if this would be helpful or not.

There is also the possibility of storing the pending Promises centrally, and only executing the rendered() template function once they have all resolved. This seems a bit more complicated with Pug though, as the tag methods are exposed directly as data vars, since Pug doesn't really have "tags" so to speak.