Update rubocop requirement from ~> 0.86.0 to ~> 0.87.1 (#7)

Updates the requirements on [rubocop](https://github.com/rubocop-hq/rubocop) to permit the latest version.
- [Release notes](https://github.com/rubocop-hq/rubocop/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop@v0.86.0...v0.87.1)

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Marc Qualie <[email protected]>

Author: dependabot[bot]

.rubocop.yml

@@ -11,6 +11,8 @@ Metrics/MethodLength:
     - test/**/*_test.rb
 Style/TrailingCommaInArguments:
   EnforcedStyleForMultiline: consistent_comma
+Style/AccessorGrouping:
+  EnforcedStyle: separated
 
 Layout/LineLength:
   Exclude:

Gemfile

@@ -7,4 +7,4 @@ gemspec
 
 gem 'minitest', '~> 5.0'
 gem 'rake', '~> 13.0'
-gem 'rubocop', '~> 0.86.0'
+gem 'rubocop', '~> 0.87.1'