Allow lambda for dynamic setup to work.

Per https://github.com/intridea/omniauth/wiki/Adapting-strategies-for-1.0 
The overriding def initializer is removed and the functionality around the use of the :url option with it.

BREAK :url option as the using it required overriding super.initialize which broke using dynamic setup with lambdas.

ADD :path option to handle CAS servers running suburi like on /cas
ADD restructure (delete code) to allow lambdas to work for dynamic setup