message: Prepare 2.3.0 release
diff: # Change Log
  -## Unreleased
  +## [v2.3.0](https://github.com/Polymer/dom5/tree/v2.3.0) (2017-05-03)
  - **Added** `insertAfter()` function
  ## [v2.2.0](https://github.com/Polymer/dom5/tree/v2.2.0) (2017-04-14)
  