message: Prepare CHANGELOG for 3.0.0-pre.15 release.
diff: @@ -5,7 +5,10 @@ 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
  +<!-- ## Unreleased -->
  +<!-- Add new, unreleased changes here. -->
  +
  +## [3.0.0-pre.15] - 2018-03-15
  * Now recognizes classes, behaviors, elements, and mixins that are
  declared in an ES6 `export` declaration.
  * Document#getFeatures now supports querying by `statement`. Given the
  @@ -19,7 +22,6 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
  * Fixed issue where FsUrlResolver and IndirectUrlResolver didn't correctly
  resolve protocol-relative URLs. These classes now accept a protocol option
  which defaults to `https` that is prepended when resolving these URLs.
  -<!-- Add new, unreleased changes here. -->
  ## [3.0.0-pre.14] - 2018-03-09
  * [BREAKING] JavascriptDocument#ast is now a `babel.File` rather than a
  