`split(//u)` works correctly with multibyte characters under 1.8, but I'm not sure how to make mutant pass.

```
Alive: rspec:Yardstick::Rules::Summary::Length#valid?:/Users/indrek/yardstick/lib/yardstick/rules/summary.rb:45:75b73 (0.11s)
@@ -1,4 +1,4 @@
 def valid?
-  ((summary_text.split(//u).length) <= (MAXIMUM_LINE_LENGTH))
+  ((summary_text.length) <= (MAXIMUM_LINE_LENGTH))
 end
```
@mbj any ideas?

For 1.8 I'd make a test:
```ruby
  context 'with short summary that includes umlauts' do
    let(:text) { 'ö' * 79 }

    it { should be(true) }
  end
```

but this passes without `split(//u)` in 1.9, so the mutant thinks it is not necessary.