move all page info to app-level stores

test/apps/layout/src/client.js

@@ -2,6 +2,11 @@ import * as sapper from '@sapper/app';
 
 window.start = () => sapper.start({
 	target: document.querySelector('#sapper')
+}).catch(err => {
+	console.error(`OH NO! ${err.message}`);
+	throw err;
+}).then(() => {
+	console.log(`STARTED`);
 });
 
 window.prefetchRoutes = () => sapper.prefetchRoutes();