Upgrade onelogin/php-saml to v.2.15.0

vendor/onelogin/php-saml/CHANGELOG

@@ -1,5 +1,40 @@
 CHANGELOG
 =========
+
+v.2.15.0
+* Security improvement suggested by Nils Engelbertz to prevent DDOS by expansion of internally defined entities (XEE)
+* Fix bug on settings_example.php
+
+v.2.14.0
+* Add  parameter to the decryptElement method to make optional the formatting
+* [#283](https://github.com/onelogin/php-saml/pull/283) New method of importing a decrypted assertion into the XML document to replace the EncryptedAssertion. Fix signature issues on Signed Encrypted Assertions with default namespace
+* Allow the getSPMetadata() method to always include the encryption Key Descriptor
+* Change some Fatal Error to Exceptions
+* [#265](https://github.com/onelogin/php-saml/issues/265) Support parameters at getSPMetadata method
+* Avoid calling static method using this
+
+v.2.13.0
+* Update xmlseclibs with some fixes.
+* Add extra protection verifying the Signature algorithm used on SignedInfo element, not only rely on the xmlseclibs verify / verifySignature methods.
+* Add getAttributesWithFriendlyName method which returns the set of SAML attributes indexed by FriendlyName
+* Fix bug on parseRemoteXML and parseFileXML. Internal calls to parseXML missed the desiredNameIdFormat parameter
+
+v.2.12.0
+* Improve Time management. Use DateTime/DateTimeZone classes.
+* Escape error messages in debug mode
+* Improve phpdoc
+* Add an extra filter to the url to be used on redirection
+
+* [#242](https://github.com/onelogin/php-saml/pull/242) Document that SHA-1 must not be used
+* [#250](https://github.com/onelogin/php-saml/pull/250) Fixed issue with IdPMetadataParser only keeping 1 certificate when multiple certificates of a single type were provided.
+* [#263](https://github.com/onelogin/php-saml/issues/263) Fix incompatibility with ADFS on SLO. When on php saml settings NameID Format is set as unspecified but the SAMLResponse has no NameID Format, no NameID Format should be specified on LogoutRequest.
+
+v.2.11.0
+* [#236](https://github.com/onelogin/php-saml/pull/236) Exclude unnecesary files from Composer production downloads
+* [#226](https://github.com/onelogin/php-saml/pull/226) Add possibility to handle nameId NameQualifier attribute in SLO Request
+* Improve logout documentation on Readme.
+* Improve multi-certificate support
+
 v.2.10.7
 * Fix IdPMetadataParser. The SingleLogoutService retrieved method was wrong
 * [#201](https://github.com/onelogin/php-saml/issues/201) Fix issues with SP entity_id, acs url and sls url that contains &