Add missing info on 1.15.1 release

docs/simplesamlphp-changelog.md

@@ -27,6 +27,19 @@ Released TBD
 ### Sqlauth
   * Changed from default-enabled to default-disabled.
 
+## Version 1.15.1
+
+Released 2018-01-12
+
+### Bug fixes
+  * AuthX509 error messages were broken.
+  * Properly calculate supported protocols based on config.
+  * NameIDAttribute filter: update to use SAML2\XML\saml\NameID.
+  * Replace remaining uses of SimpleSAML_Logger with namespace version.
+  * Statistics: prevent mixed content errors.
+  * Add 'no-store' to the cache-control header to avoid Chrome
+    caching redirects.
+
 ## Version 1.15.0
 
 Released 2017-11-20