Update CHANGELOG.md

Co-Authored-By: tisba <tisba@users.noreply.github.com>

Author: mattbrictson

CHANGELOG.md

@@ -5,6 +5,7 @@ appear at the top.
 
 ## [Unreleased][]
 
+  * Your contribution here!
   * [#448](https://github.com/capistrano/sshkit/pull/448): Fix misbehaving connection eviction loop when disabling connection pooling - [Sebastian Cohnen](https://github.com/tisba)
 
 ## [1.18.1][] (2019-01-26)