Polish

- upgrade to reactor M3
- re-introduce html5 shim
- polish controller
Re-enable sockjs sess cookies (now false by default)
Remove setting for cookie_needed

It's not set by default in the SockJS Service:
https://github.com/spring-projects/spring-framework/commit/77fa8698b3687d20c2750562778f3a35b0048320
Polish index.html

Fix typos and improve punctuation