* extends KonovaSSOClient for providing support of propagated user data from sso-server. For longterm, we hope to have this feature directly on django-simple-sso. Further details can be found here: https://github.com/divio/django-simple-sso/issues/67
* removes unused third party package from requirements.txt
* adds KonovaSSOClient as subclass of sso.Client for more control over login, e.g. which user data shall not be updated (found in konoa/sso/sso.py)
* adds Messenger class for communicating with SSO server (found in konova/utils/messenger.py)