CAS 3.0 support

CAS 3.0 support

To support CAS 3.0,the attribute mapper should be like:

```python

def populate_user(user, authentication_response):
    if authentication_response is not None:
        if authentication_response.has_key('is_superuser'):
            user.is_superuser = authentication_response['is_superuser']

        if authentication_response.has_key('is_staff'):
            user.is_staff = authentication_response['is_staff']

        if authentication_response.has_key('givenName'):
            user.first_name = authentication_response['givenName']

        if authentication_response.has_key('sn'):
            user.last_name = authentication_response['sn']

        if authentication_response.has_key('email'):
            user.email = authentication_response['email']

    pass
```