Add integration spec for outdatedness
user
```ruby
describe 'Outdatedness integration', site: true, stdio: true do
  before do
    File.write('content/foo.md', "---\ntitle: hello\n---\n\nfoo")
    File.write('content/bar.md', '<%= @items["/foo.*"][:title] %>')

    File.write('Rules', <<EOS)
compile '/foo.*' do
  write '/foo.html'
end

compile '/bar.*' do
  filter :erb
  write '/bar.html'
end
EOS
  end

  before { Nanoc::CLI.run(%w(compile)) }

  it 'shows default rep outdatedness' do
    expect { Nanoc::CLI.run(%w(show-data --no-color)) }.to(
      output(/^item \/foo\.md, rep default:\n  is not outdated/).to_stdout,
    )
    expect { Nanoc::CLI.run(%w(show-data --no-color)) }.to(
      output(/^item \/bar\.md, rep default:\n  is not outdated/).to_stdout,
    )
  end

  it 'shows file as outdated after modification' do
    File.write('content/bar.md', 'JUST BAR!')

    expect { Nanoc::CLI.run(%w(show-data --no-color)) }.to(
      output(/^item \/foo\.md, rep default:\n  is not outdated/).to_stdout,
    )
    expect { Nanoc::CLI.run(%w(show-data --no-color)) }.to(
      output(/^item \/bar\.md, rep default:\n  is outdated: /).to_stdout,
    )
  end

  it 'shows file and dependencies as not outdated after content modification' do
    File.write('content/foo.md', "---\ntitle: hello\n---\n\nfoooOoooOOoooOooo")

    expect { Nanoc::CLI.run(%w(show-data --no-color)) }.to(
      output(/^item \/foo\.md, rep default:\n  is outdated: /).to_stdout,
    )
    expect { Nanoc::CLI.run(%w(show-data --no-color)) }.to(
      output(/^item \/bar\.md, rep default:\n  is not outdated/).to_stdout,
    )
  end

  it 'shows file and dependencies as outdated after title modification' do
    File.write('content/foo.md', "---\ntitle: bye\n---\n\nfoo")

    expect { Nanoc::CLI.run(%w(show-data --no-color)) }.to(
      output(/^item \/foo\.md, rep default:\n  is outdated: /).to_stdout,
    )
    expect { Nanoc::CLI.run(%w(show-data --no-color)) }.to(
      output(/^item \/bar\.md, rep default:\n  is outdated: /).to_stdout,
    )
  end
end
```
assistant