Shibboleth administration guide

This is a draft article for explaining a basic shibboleth identity provider install and configuration.

**edit**: [Rendered](https://github.com/jch/saml/blob/shibboleth-administration/shibboleth-administration.md)

cc @michaeltwofish @mtodd @sbryant @lildude
I think we should give more of a clue as to the location of this file.