Support assertion conditions NotBefore and NotOnOrAfter validation
Merge remote-tracking branch 'origin/assertion-conditions-timestamps'
Support -1 for acceptedClockSkew to disable timestamp validity checks, use default of 0 for acceptedClockSkew
Merge from bergie/passport-saml master
Additional support to check NotBefore and NotOnOrAfter as part of SubjectConfirmation element
Merge branch 'mradamlacey-notbefore-notonorafter'
Cleanup of merge of PR #38.