Dutch translation fix

The strings file translated "hourse" to "uren" which is correct dutch but not in this case. When the dutch say "Hours ago" we still use the single "hour" instead of "hours". So it should be "uur" not "uren".

In order to use this fork in your podfile use this until this pull request is approved.
```
pod 'SORelativeDateTransformer', :git => 'https://github.com/renssies/SORelativeDateTransformer.git'
```