message: Updated CHANGELOG for new 2.0.0-pre.12 version.
diff: @@ -5,7 +5,7 @@ All notable changes to this project will be documented in this file.
  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.12 - 2017-04-14
  - BREAKING: Public API change. The `bundle()` method now takes a manifest
  instead of entrypoints, strategy and mapper. To produce a manifest,
  use new public method `generateManifest()`.
  