message: Updated CHANGELOG for 3.4.0 release.
diff: @@ -6,9 +6,11 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
  and this project adheres to [Semantic Versioning](http://semver.org/).
  ## Unreleased
  -* Modified the `bundle` property in project build options to support the subset of `polymer-bundler` options which can be serialized in a JSON file.
  <!-- Add new, unreleased changes here. -->
  +## [3.4.0] - 2017-06-21
  +* Modified the `bundle` property in project build options to support the subset of `polymer-bundler` options which can be serialized in a JSON file.
  +
  ## [3.3.0] - 2017-06-09
  * Removed `insertPrefetchLinks` from build presets. See https://github.com/Polymer/polymer-build/issues/239 for details.
  