update CHANGELOG

Author: agallou

CHANGELOG.md

@@ -5,6 +5,7 @@
 * [#30](https://github.com/agallou/phpstorm-plugin/pull/30) Easily identify test files via a custom icon ([@agallou])
 * [#37](https://github.com/agallou/phpstorm-plugin/pull/37) Save test and tested file before run ([@agallou])
 * [#38](https://github.com/agallou/phpstorm-plugin/pull/38) Add default keyboard shortcuts ([@agallou])
+* [#39](https://github.com/agallou/phpstorm-plugin/pull/39) Display test results as a treeView ([@agallou])
 
 ## Documentation