Fix incompatibility with OmniAuth 1.1

The `OmniAuth::Strategy#fail!` method's second argument is should be
an exception but we where passing a string. This wasn't noticed before
because earlier versions of OmniAuth just stashed that argument in the
env but now OmniAuth uses it to build a log message which fails.
remove saml code and port to ruby-saml gem.
fix up tests after ruby-saml port.
update gems.
omniauth-saml 1.0.0
Merge master. Use ruby-saml for acs metadata as well.