enable caching on static assets (close vuejs#150)

Author: yyx990803

server.js

@@ -47,9 +47,9 @@ const serve = (path, cache) => express.static(resolve(path), {
 
 app.use(compression({ threshold: 0 }))
 app.use(favicon('./public/logo-48.png'))
-app.use('/dist', serve('./dist'))
-app.use('/public', serve('./public'))
-app.use('/manifest.json', serve('./manifest.json'))
+app.use('/dist', serve('./dist', true))
+app.use('/public', serve('./public', true))
+app.use('/manifest.json', serve('./manifest.json', true))
 app.use('/service-worker.js', serve('./dist/service-worker.js'))
 
 app.get('*', (req, res) => {