Update CHANGELOG.md

Author: Brandon Olin

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [0.3.0] - Unreleased
 
+### Changed
+
+- [**#19**](https://github.com/psake/PowerShellBuild/pull/19) Allow the `BHBuildOutput` environment variable defined by `BuildHelpers` to be set via the `$PSBPreference.Build.ModuleOutDir` property of the build tasks (via [@pauby](https://github.com/pauby))
+
 ### Breaking changes
 
 - Refactor build properties into a single hashtable `$PSBPreference`