update sapper, tidy up

server.js

@@ -6,6 +6,7 @@ const static = require('serve-static');
 
 const { PORT = 3000 } = process.env;
 
+// this allows us to do e.g. `fetch('/api/blog')` on the server
 const fetch = require('node-fetch');
 global.fetch = (url, opts) => {
 	if (url[0] === '/') url = `http://localhost:${PORT}${url}`;
@@ -16,9 +17,7 @@ app.use(compression({ threshold: 0 }));
 
 app.use(static('assets'));
 
-app.use(sapper({
-	selector: '#sapper'
-}));
+app.use(sapper());
 
 app.listen(PORT, () => {
 	console.log(`listening on port ${PORT}`);