**Replace this text with a summary of the changes in your PR.
The more detailed you are, the better.**

-----------------

Before submitting the PR make sure the following are checked:

* [ ] Wrote [good commit messages][1].
* [ ] Commit message starts with `[Fix #issue-number]` (if the related issue exists).
* [ ] Feature branch is up-to-date with `master` (if not - rebase it).
* [ ] Squashed related commits together.
* [ ] Added tests.
* [ ] Added an entry to the [Changelog](../blob/master/CHANGELOG.md) if the new code introduces user-observable changes. See [changelog entry format](../blob/master/CONTRIBUTING.md#changelog-entry-format).
* [ ] The PR relates to *only* one subject with a clear title
  and description in grammatically correct, complete sentences.
* [ ] Run `bundle exec rake default`. It executes all tests and RuboCop for itself, and generates the documentation.

[1]: https://chris.beams.io/posts/git-commit/

**Replace this text with a summary of the changes in your PR.
The more detailed you are, the better.**

-----------------

Before submitting the PR make sure the following are checked:

* [ ] Wrote [good commit messages][1].
* [ ] Commit message starts with `[Fix #issue-number]` (if the related issue exists).
* [ ] Feature branch is up-to-date with `master` (if not - rebase it).
* [ ] Squashed related commits together.
* [ ] Added tests.
* [ ] Added an entry to the [Changelog](https://github.com/rubocop-hq/rubocop/blob/master/CHANGELOG.md) if the new code introduces user-observable changes. See [changelog entry format](https://github.com/rubocop-hq/rubocop/blob/master/CONTRIBUTING.md#changelog-entry-format).
* [ ] The PR relates to *only* one subject with a clear title
  and description in grammatically correct, complete sentences.
* [ ] Run `bundle exec rake default`. It executes all tests and RuboCop for itself, and generates the documentation.

[1]: https://chris.beams.io/posts/git-commit/

Use URL instead of relative path for documents in the repository
Use URL instead of relative path for documents in the repository

This is a cosmetic documentation change.

This PR uses URL instead of relative path for documents in the
repository

404 page will be displayed when trying to refer to "Changelog" link and
"changelog entry format" link in the following URL.
https://github.com/rubocop-hq/rubocop/blob/master/.github/PULL_REQUEST_TEMPLATE.md

Therefore, This PR changed from relative path to URL.
