Static-frame

Added ``Frame.to_npy()``, ``Frame.from_npy()`` with a `memory_map` option.

Improvements to ``Frame.to_npz()`` to support large files and buffered writes.

Performance enhancements to all ``_StoreZip`` subclasses through usage of ``WeakValueDictionary`` caching.

Added ``IndexHiearchy.relabel_at_depth()``.

Added support for string slicing and selection with ``Series.via_str[]`` and ``Frame.via_str[]``.

Reimplemented ``Frame.to_npz()``, ``Frame.from_npz()``, removing support for object arrays (and pickles) and improving performance.

Added ``Bus.to_zip_npz()``, ``Bus.from_zip_npz()``, ``Quilt.to_zip_npz()``, ``Quilt.from_zip_npz()``, ``Batch.to_zip_npz()``, ``Batch.from_zip_npz()`` and ``Yarn.to_zip_npz()``.

Implemented ``Series.fillfalsy_forward()``, ``Series.fillfalsy_backward()``, ``Series.fillfalsy_leading()``, ``Series.fillfalsy_trailing()``.

Implemented ``Frame.fillfalsy_forward()``, ``Frame.fillfalsy_backward()``, ``Frame.fillfalsy_leading()``, ``Frame.fillfalsy_trailing()``.

Added ``Quilt.equals()``.

``Frame.from_pandas()`` now supports zero-sized DataFrame.

Fixed issue in ``Frame.set_index()`` where ``column`` is passed as ``None``.

Removed ``TypeBlocks._block_slices``.

Frame.to_pandas()`` now creates ``pd.RangeIndex`` for ``IndexAutoFactory``-created indices.

Performance enhancements to ``Frame.from_concat()``.

Corrected issue extracting containers stored in ``Series``.

Improved dtype resolution on ``Frame`` methods that reduce dimensionality.

Corrected issue where summing a ``Frame`` of Booleans along axis 0 resulted in Booleans instead of integers.