default config: only include paths relative to cwd

[ushi-as]

The default include patterns also matched folders outside the current working directory. When my app lives in /srv/app the pattern **/app/**/*.rb also matches the file spec/rails_helper.rb, because the absolute path (/srv/app/spec/rails_helper.rb) matches the pattern. This is unintended. The PR ensures that only app folders inside the projects directory are recognized.

Before submitting the PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Wrote good commit messages.
• 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.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.
• If this is a new cop, consider making a corresponding update to the Rails Style Guide.