add changelog

CHANGELOG.md

@@ -0,0 +1,6 @@
+# Change log
+
+All notable changes to the project will be documented in this file. This project adheres to [Semantic Versioning](http://semver.org).
+
+## [1.0.0] - 2019-05-31
+Initial release of this fork. The only change from the upstream code is https://github.com/launchdarkly/go-ntlmssp/pull/1.