Update saml2 library

Author: baszoetekouw

composer.json

@@ -34,7 +34,7 @@
         "ramsey/uuid": "^3.3.0",
         "sensio/framework-extra-bundle": "^3.0",
         "sensio/generator-bundle": "^3.0",
-        "simplesamlphp/saml2": "4.16.*",
+        "simplesamlphp/saml2": "4.17.*",
         "swiftmailer/swiftmailer": "^5.4",
         "symfony/monolog-bundle": "^3.1.0",
         "symfony/swiftmailer-bundle": "^2.6",