Idea: Option to use the same DB as Sopel

[dgw]

It's understandable that this plugin was hardcoded to use MySQL, because that's what its daddy https://github.com/zigdon/xkcd-Bucket uses. But Sopel uses SQLAlchemy to support all kinds of database backends now (thanks to your own work, Rusty!) and it would be great if, at least for new users, this plugin could just drop in and work without having to set up a MySQL database just for it.