Merge pull request #10 from xcompass/master

Add basic support for CAS 2.0 and CAS 3.0
Refactored test_routing tests

* Moved tests into three classes one for each CAS version
* Minor formating changes
Updated README with new configuration options
Merge pull request #11 from xcompass/master

Fix incorrect close statement
Add return URL after logout

The logout URL accepts a parameter (url or service) to redirect user
back after logging out from CAS server.
https://github.com/Jasig/cas/blob/master/cas-server-protocol/3.0/cas_protocol_3_0.md#231-parameters