Redirect loop in SAML

[Akshay Pinto]

Flask-saml now pulls in werkzeug 0.15.1 which changed proxyfix

ProxyFix in werkzeug.contrib.fixers is deprecated in favour of from werkzeug.middleware.proxy_fix import ProxyFix

This causes flask-saml to break. The /saml/acs/ endpoint does not return the SET_COOKIE header which causes the application to enter an infinite loop with the saml provider and the application