Turn off escaping for numberdiff as output may contain HTML

There's an issue with escaping output in case of numberdiff jelly template. This causes following:

![screen shot 2013-12-03 at 18 35 07](https://f.cloud.github.com/assets/287584/1669063/72b2a51a-5c70-11e3-8c5f-b3218dab1bea.png)

I believe we can turn off escaping for this specific case and template.