message: docs: add changelog for 3.1.2
diff: +<a name="3.1.2"></a>
  +## [3.1.2](https://github.com/NativeScript/nativescript-angular/compare/3.1.1...3.1.2) (2017-07-12)
  +
  +
  +### Bug Fixes
  +
  +* **renderer:** attach `CommentNode`s to visual tree ([#888](https://github.com/NativeScript/nativescript-angular/issues/888)) ([65359fa](https://github.com/NativeScript/nativescript-angular/commit/65359fa)), closes [#872](https://github.com/NativeScript/nativescript-angular/issues/872)
  +
  +
  +
  <a name="3.1.1"></a>
  ## [3.1.1](https://github.com/NativeScript/nativescript-angular/compare/3.1.0...3.1.1) (2017-06-29)
  