Fix 304 with browser reloads

src/libs/app.js

@@ -34,6 +34,10 @@ app.use((req, res, next) => {
     req.sql = squel.select();
     next();
 });
+app.use((req, res, next) => {
+    res.setHeader('Last-Modified', (new Date()).toUTCString());
+    next();
+});
 // Mounts all API routes under /api/v1
 app.use('/api/v1', api);