I refreshed my instance with the latest code from the master branch.
Via XMLUI, I am able to successfully login with Shibboleth.
Via REST, I opened /rest/login-shibboleth. I was re-directed to my Shibboleth authentication page.
After providing my credentials, I received a failed login. Note the following message in my dspace log.
2016-03-23 17:31:04,730 ERROR org.dspace.authenticate.ShibAuthentication @ Shibboleth authentication was not able to find a NetId, Email, or Tomcat Remote user for which to indentify a user fro
2016-03-23 17:31:04,730 ERROR org.dspace.authenticate.ShibAuthentication @ Unable to register new eperson because we are unable to find an email address along with first and last name for the u
NetId Header: 'uid'='null' (Optional)
Email Header: 'mail'='null'
First Name Header: 'givenName'='null'
Last Name Header: 'sn'='null'
2016-03-23 17:31:04,730 INFO org.dspace.rest.authentication.DSpaceAuthenticationProvider @ anonymous::failed_login:email=, result=4