Implements Multiclass hinge loss

Implements multiclass hinge loss. Fixes #3451 
I had meant

    mask = label_vector == y
    pos_label_index = np.where(mask)[0][0]
    neg_label_indices = np.where(~mask)[0][0]

However please try implementing this way https://github.com/scikit-learn/scikit-learn/pull/3607/files#r16925342