Corrected "sucess" to "success"
Added new signals.
Sending login failure signal when no user has been authenticated inside a POST.
Validation failure now sends signal

Added service arg to the _cas2_error_response helper.
Sending proxy success signal.
Sending validation success signal.
Added version arg to validation signals to differentiate v1 and v2 protocols.
Merge pull request #1 from Crossway/feature/extra-signals

Added extra signals for auth-related actions