Polish pom.xml and README
Switch back to 4.0 snapshots

Due to Tomcat change
Add Cache-Control to index.html

index.html shoud not be cached since it is behind authentication.
caching it can interfere with sockjs requests
Update README.md
Update to latest Spring Framework 4.0 snapshot changes
Update to latest snapshot (use SubProtocolHandler)
Spring Integration-based version of the sample

Rework the sample to use Spring Integration's Spring 4-based WebSocket
and STOMP support.