Update PR template with version requirement

Author: pirj

.github/PULL_REQUEST_TEMPLATE.md

@@ -8,11 +8,16 @@ Before submitting the PR make sure the following are checked:
 * [ ] Squashed related commits together.
 * [ ] Added tests.
 * [ ] Updated documentation.
-* [ ] Added an entry to the [changelog](https://github.com/rubocop-hq/rubocop-rspec/blob/master/CHANGELOG.md) if the new code introduces user-observable changes.
+* [ ] Added an entry to the `CHANGELOG.md` if the new code introduces user-observable changes.
 * [ ] The build (`bundle exec rake`) passes (be sure to run this locally, since it may produce updated documentation that you will need to commit).
 
 If you have created a new cop:
 
 * [ ] Added the new cop to `config/default.yml`.
 * [ ] The cop documents examples of good and bad code.
 * [ ] The tests assert both that bad code is reported and that good code is not reported.
+* [ ] Set `VersionAdded` in `default/config.yml` to the next minor version.
+
+If you have modified an existing cop's configuration options:
+
+* [ ] Set `VersionChanged` in `default/config.yml` to the next major version.