Merge pull request go-cas#3 from yp-engineering/attributes_extras

Update XML Service Response support for latest CAS SAML extra attributes.

The [specification][spec] for the SAML CAS response attributes has been changed such that the `cas:attributes` XML element no longer mentions the `cas:userAttributes` element. The contents of the `cas:userAttributes` element can now be located directly in the `cas:attributes` element.

[spec]: http://jasig.github.io/cas/4.1.x/protocol/CAS-Protocol-Specification.html#saml-cas-response-attributes

gopkg.in/cas.v1: v1.0.2

Add support for X-Forwarded-Proto when building the Service request URL.

This is considered a non-breaking change which should fix expected behaviour and so has not resulted in a v2 release.

Bump to remove mistakenly included RedirectToCas function

Version 1.0