Add Support For RaiseEvent on Groups

We should have the possibilty to raise an event on defined groups.
Project Update to VS2012
Dont Json Stringify the Subject

This fix needs to be done because of an TypeError: Converting circular structure to JSON
See : https://github.com/ianreah/SignalR.Reactive/commit/9d3332dad25d64a96eb5197e27419bd543cf2e81
Merge pull request #7 from straeger/master

Raise Events on Groups