Format hours in FormattingUtils

Eurgh, I really hate this code. And funnily enough line breaks *before* a minus
sign will just silently break. A line starting with "-" is going to be ignored.
WTF?
Probably also want to sum up, so:

```
Map times = lines.groupBy { it[0] }.collectEntries { k, v -> [k, v.sum()] }
```

But I think this might be very Groovy 1.8 specific.