add git readme

git-svn-id: https://plugins.svn.wordpress.org/shibboleth/trunk@889045 b8457f37-d9ea-0310-8a92-e5e31aec5664
initial fixes from 2012

git-svn-id: https://plugins.svn.wordpress.org/shibboleth/trunk@889046 b8457f37-d9ea-0310-8a92-e5e31aec5664
use the capability manage_options instead of administrator

git-svn-id: https://plugins.svn.wordpress.org/shibboleth/trunk@889047 b8457f37-d9ea-0310-8a92-e5e31aec5664