message: Updated CHANGELOG for 2.0.0-pre.18 release.
diff: @@ -8,6 +8,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
  <!-- ## Unreleased -->
  <!-- Add new, unreleased changes here. -->
  +## 2.0.0-pre.18 - 2017-05-15
  +- Updated dependency on `polymer-analyzer` to ^2.0.0 now that it is
  + out of alpha.
  +
  ## 2.0.0-pre.17 - 2017-05-11
  - BREAKING: Bundler's `bundle()` method now returns a `BundleResult`
  instead of just a document collection. It does this to include a
  