[MRG] Implements Multiclass hinge loss

Implements multiclass hinge loss. Fixes #3451 
Option 1:
```python
        if (labels is None and len(pred_decision.shape) > 1 and
                not np.array_equal(y_lab, np.arange(pred_decision.shape[1]))):
```

Option 2
```python
        if labels is None and len(pred_decision.shape) > 1 and \
                (not np.array_equal(y_lab, np.arange(pred_decision.shape[1]))):
```

PEP8 is designed to make code be readable. There is no point following PEP8 in a way that makes the code unreadable.