Update README.md
Fix issue with multifactor authentication request not recognizing existing authentication session.

This commit does NOT address the use case where CAS is ought to remember the authentication method. This commit merely addresses the issue of missing authentication context in the event that TGT is considered invalid.
Merge branch 'master' of github.com:Unicon/cas-mfa
Javadocs: Update the Javadocs on the MFA CAS Impl to better explain its purpose.
Update README.md
Update README.md
Update README.md
Modify the CAS server to be able to remember the authentication method used.

Appropriately modify the CAS protocol to return the authentication method in the validation payload, or decorate correct error messages based on the requested method.
Modify the mfa authentication request to be able to conditionally require mfa.

Added additional tests in support of new behavior.
Added authentication method along with user attributes to the validation xml response.
trivial: request --> requested in JavaDoc
Remove rebel.xml from the codebase.
Rename ServiceValidateController. Address code reviews.
Merge branch 'REMEMBER_AUTHN_METHOD' of github.com:Unicon/cas-mfa into REMEMBER_AUTHN_METHOD
Fix test failures on the spec validation.
Fix a typo, and correct the javadoc in a few spots.
Document how to build cas-mfa-java
Documents CAS server GH issue requesting non-final
Documents with URL the CAS server GitHub issue requesting non-final SimpleWebApplicationServiceImpl which would simplify this class.
trivial: "can be retrieve" --> "can be retrieved"
clarifies JavaDoc of Validate...MFARequestAction