[RFC] fix sorting issue with newer nose version

This is just an attempt to fix the issue with newer versions of nose.
Nose plugin manager uses this `sort()` method to sort the plugins : 
```python
def sort(self):
        return sort_list(self._plugins, lambda x: getattr(x, 'score', 1), reverse=True)
```
So I thought that setting a high score would be enough.

Unfortunately with my changes, tests are not even run... I'll continue to look at it. Do you have any suggestion ?