Add changelog and update readme

Author: rroemhild

CHANGELOG.md

@@ -0,0 +1,22 @@
+# Changelog
+
+
+## v2.1 (rroemhild/test-openldap:2.1)
+
+* Re-add PR #14: add_config_admin_pw
+
+
+## v2.0 (rroemhild/test-openldap:2.0)
+
+* Set ports higher than 10000 (10389 / 10636)
+* Set user in dockerfile
+* Use tini to start slapd
+* Use CMD for slapd arguments
+
+
+### Breaking changes
+
+Different port numbers than in the version before
+
+* 380 -> 10389
+* 686 -> 10686