Updated links; CAS is moving from Jasig to Apereo.
Added notes about running txcas on a Raspberry Pi.
BUGFIX: `jinja2_view_provider.py` error when no service manager.

Was returning a raw dict instead of a deferred when there was no service
manager passed to the view provider.
Added tasks for Jinja2ViewProvider; refactored User class from various realm impls.
Added IServiceAcceptor interface; LDAPRealm can alias attributes and select them based on service.
Updated docs for `LDAPRealm` to include alias and service-registry options.
Added "Server App Init Test".
Added tests for /validate and /serviceValidate.
Added /proxyValidate test (no pgtUrl).
Added test for presenting invalid credentials; server *should* return 403 on failure.
Test to prove login ticket must be for a specific service.
Added some additional logging to failed ticket validations.
Added test for bad /validate.
Added tests for /serviceValidate and /proxyValidate with bad services.
Added test for /login (GET) to make sure  service is valid.
Added test for using TGC.
Adapted TGC tests to /serviceValidate and /proxyValidate.
Added test for /logout.
Added docs on running the unit tests.
Intermediate development for client cert auth.

In progress.