After writing the comment about `AddCustomHandler`, I realized I feel similarly about `AddStaticFiles`.

These are definitely useful functions, but my vision for `sleepy` is more as a decently-featured, very simple way to route HTTP requests to certain endpoints to functions matching the HTTP method of the request. Providing in-library support for serving static files and adding custom handlers feels like it's straying from that vision a little too much.

I love the `mux()` function. That's a nice design. I think that exporting that function would provide consumers of `sleepy` all of the access they need to add custom features that these functions add to their RESTful API.

Thanks so much for these contributions. I'd love to hear counterpoints, but as it stands I'm in favor of dropping these two functions, changing `mux()` to `Mux()` and I'd go ahead and merge.