message: docs: add changelog for 4.2.0
diff: +<a name="4.2.0"></a>
  +# [4.2.0](https://github.com/angular/angular/compare/4.2.0-rc.2...4.2.0) salubrious-stratagem (2017-06-08)
  +
  +
  +### Bug Fixes
  +
  +* **animations:** ensure web-animations understands a numeric CSS perspective value ([819514a](https://github.com/angular/angular/commit/819514a)), closes [#14007](https://github.com/angular/angular/issues/14007)
  +* **animations:** evaluate substitutions on option param values ([e9886d7](https://github.com/angular/angular/commit/e9886d7))
  +* **forms:** fix min and max validator behavior on non-numbers ([a222c3e](https://github.com/angular/angular/commit/a222c3e))
  +* **router:** opening links in new window ([4c32cb9](https://github.com/angular/angular/commit/4c32cb9))
  +* **upgrade:** call setInterval outside the Angular zone ([269bbe0](https://github.com/angular/angular/commit/269bbe0))
  +
  +
  +### Features
  +
  +* **compiler-cli:** introduce synchronous codegen API ([b00b80a](https://github.com/angular/angular/commit/b00b80a))
  +
  +
  +### Performance Improvements
  +
  +* **animations:** do not create a closure each time a node is removed ([fe6b39d](https://github.com/angular/angular/commit/fe6b39d))
  +* **animations:** only apply `:leave` flags if animations are set to run ([b55adee](https://github.com/angular/angular/commit/b55adee))
  +
  +
  +
  <a name="4.2.0-rc.2"></a>
  # [4.2.0-rc.2](https://github.com/angular/angular/compare/4.2.0-rc.1...4.2.0-rc.2) (2017-06-01)
  