message: Updated CHANGELOG for 2.0.0-pre.6 release.
diff: @@ -6,6 +6,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
  and this project adheres to [Semantic Versioning](http://semver.org/).
  ## Unreleased
  +
  +## 2.0.0-pre.6 - 2017-02-17
  - Handle `<base href="...">` values correctly when inlining imports.
  - Apply `<base target="...">` to links and forms in the same document as
  appropriate.
  