Use tuple sequences for multidimensional array indexing
On Travis CI [logs](https://travis-ci.org/pandas-dev/pandas/jobs/415610906) we get the below warning ( 4 times):

pandas/tests/series/indexing/test_datetime.py::test_getitem_median_slice_bug
  /home/travis/build/pandas-dev/pandas/pandas/core/internals/blocks.py:301: FutureWarning: Using a non-tuple sequence for multidimensional indexing is deprecated; use `arr[tuple(seq)]` instead of `arr[seq]`. In the future this will be interpreted as an array index, `arr[np.array(seq)]`, which will result either in an error or a different result.

If possible we should upgrade to using tuples here.

I will follow up with a PR unless anyone has any concerns.

Thanks,