message: Update CHANGELOG to include v0.16.0-beta.2
diff: # Changelog
  +## v0.16.0-beta.2 (2019-03-14)
  +
  +#### :rocket: Enhancement
  +* `@orbit/store`
  + * [#596](https://github.com/orbitjs/orbit/pull/596) Add Store.rebase() ([@Bernhard---H](https://github.com/Bernhard---H))
  +
  +#### :bug: Bug Fix
  +* `@orbit/record-cache`
  + * [#603](https://github.com/orbitjs/orbit/pull/603) Return empty array when querying for non-existing relationships with findRelatedRecords ([@PieterJanVdb](https://github.com/PieterJanVdb))
  +
  +* `@orbit/record-cache`
  + * [#605](https://github.com/orbitjs/orbit/pull/605) Extends #603 to fix related errors ([@dgeb](https://github.com/dgeb))
  +
  +#### :house: Internal
  +* `@orbit/store`
  + * [#604](https://github.com/orbitjs/orbit/pull/604) Cleanup and extend store tests ([@dgeb](https://github.com/dgeb))
  +
  +#### Committers: 3
  +- Bernhard Halbartschlager ([@Bernhard---H](https://github.com/Bernhard---H))
  +- Pieter-Jan Vandenbussche ([@PieterJanVdb](https://github.com/PieterJanVdb))
  +- Dan Gebhardt ([@dgeb](https://github.com/dgeb))
  +
  +
  ## v0.16.0-beta.1 (2019-02-10)
  #### :boom: Breaking Change
  