Conflicts:
	lib/omniauth/strategies/cas.rb

Its worth noting that this upgrade was affected by intridea/omniauth#724

This makes the code a bit more self-documenting

Also, expose a `nickname_key` setting, defaulting to 'user'.

More options for values handed back by CAS.  This is needed because
different auth strategies for CAS sometimes hand back different
keys for these items.  They're not configurable on an application
basis.  Only globally.  This means omniauth-cas needs to be more
flexible and setting defaults while you're at it.

This allows them to share the same describe block

This whole pull request is essentially a revert of 577e2386 and #11