Enhanced offline (#249)

* Notification of updates & reloading

* Using version in service worker & allowing version to appear elsewhere

* Stupid file

* Ditching changelog for now. Using package json.

* Ugh.

src/missing-types.d.ts

@@ -32,3 +32,5 @@ declare module 'url-loader!*' {
   const value: string;
   export default value;
 }
+
+declare var VERSION: string;