Enhanced support for ``fill_value`` as a ``FillValueAuto``, a mapping, or a sequence of fill values (per column) where appropriate.
Added ``Index.dropna()``, ``Index.dropfalsy()``, ``IndexHierarchy.dropna()``, ``IndexHierarchy.dropfalsy().
Added ``Index.fillfalsy()``, ``IndexHierarchy.fillfalsy()``.
Performance improvements for ``Frame.iter_group_labels()``, ``Frame.iter_group_labels_items()``, ``Frame.iter_group_labels_array()``, ``Frame.iter_group_labels_array_items()``.
Fixed usage of ``dtypes`` argument when encountering zero-sized data in ``Frame.from_records()`` and ``Frame.from_pandas()``.
Improved ``Frame.iter_tuple`` to not coerce types through arrays.
Added ``Frame.set_columns()``, ``Frame.set_columns_hierarchy()``, and ``Frame.unset_columns()``.