Fix shuffle for arrays with ndim > 2: added a allow_nd as an acceptable parameter to resample.

Fixes https://github.com/scikit-learn/scikit-learn/issues/3694 by passing allow_nd=True into check_array within resample and shuffle, allowing shuffle and resample to work on arrays with ndim > 2. Also added a short test for shuffling an array with ndim = 3.
Given that we are only shuffling two items, this will only be true 50% of the time. You haven't fixed a random state, so this will mean our automatic tests will fail 50% of the time. I think it's fine to leave this condition off. We only need a smoke test.