Modified the Cas Adapter to return a type of CasResult (Issue: 1)

Modified the Cas Adapter to return a type of CasResult (extending Zend's Result Class). 

This new Result class contains the body of the CAS Result, such that systems requiring additional or custom information from the CAS result can extend the CasAdapter and read custom response information from the CasResult.

https://github.com/tillikum/zf2-cas-authentication-adapter/issues/1