[MRG] Added metrics support for multiclass-multioutput classification

Fix for #3453 
Ping @arjoly . Added support for `zero_one_loss` and `accuracy_score`

I don't think this is pep8. It's better to avoid the `\`. I would do

```
            if (merged_type.startswith('multilabel') or 
                   merged_type == 'multiclass-multioutput)':
                blah...
```