Update CHANGELOG.md with description of changes.

Author: James Foster

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 ### Added
+- Added `Client.h`, `IPAddress.cpp`, `IPAddress.h`, `Printable.h`, `Server.h`, `Udp.h` and test to see that they are usable.
 
 ### Changed
 - Move repository from https://github.com/ianfixes/arduino_ci to https://github.com/Arduino-CI/arduino_ci