First

In this release

1. Caches only urls. Images and other assets should be the concern of browsers
2. First, returns cached version of url.
3. After that, makes a fetch request on background to that url.
4. If there is any difference between cached and remote html, then updates it on background and sends a message to client
5. When client gets a message to refresh, it can reload the page or load via js (example: jQuery load function)