Added ``NPY`` and ``NPZ`` interfaces for creating NPY and NPZ archvies from arrays and ``Frame`` components.
Added ``index_constructors`` argument to ``IndexHierarchy.from_product()``
Added ``index_constructor`` argument to ``Index.level_add()``, ``IndexHierarchy.level_add()``, and ``Frame.relabel_level_add()``.
Added ``index_constructor``, ``columns_constructor`` arguments to ``Frame.relabel()``.
Added ``Series.to_frame_he()``.
Added ``index``, ``index_constructor``, ``columns``, ``columns_constructor`` arguments to ``Series.to_frame()``, ``Series.to_frame_go()``, ``Series.to_frame_he()``.
Improvement to ``Frame.from_concat`` to avoid creating one-element indices from ``Series`` when an index is provided along the appropriate axis.
Added ``index_constructor`` argument to ``Series.relabel()``.
Added ``index_constructor`` argument to ``Series.from_concat()``.
Added ``index`` argument to ``Series.from_pandas()``.
Added ``index`` and ``columns`` argument to ``Frame.from_pandas()``.
Improvement to ``Index`` initialization to raise ``ErrorInitIndex`` if given a single string as ``labels``.
Set operations on labels of different ``datetime64`` units now raise an ``Exception``.