Allow to keep un-namespaced attributes AND attributes with "cas" prefix

[nox-404]

It will keep all attributes into extra_attributes["cas"]

[nox-404]

This allow rack-cas to work with CAS like the one from web2py

[adamcrown]

Thanks for putting the work in on this @nox-404. I wasn't aware that web2py used CAS authentication so that's good to know.

There are enough different CAS implementations that I'm thinking I need to stop trying to have the code figure out which one is which automatically, and instead have different "plugins" for each different type of extra attributes format. So I'm thinking I'll hold off on merging this in favor of that approach.

I'll leave this open until I have a solution in place though. If it takes me a while then I'll come back and merge this in.

[nox-404]

Ok thanks