Don't send duplicate messages.

Switch to using watch because watchCollection because of https://github.com/angular/angular.js/issues/2621
Allows us to see when the value changes.

Note - this does not fully fix bug 15, - there is either a bug in django-websocket-redis or we are using it incorrectly.   

Symptom:  if you edit a field quickly, the the server will continually send us the last few edits.