Static-frame

Performance enhancements to ``Frame.from_npy`` and ``Frame.from_npz``.

Added ``Frame.to_pickle()``, ``Frame.from_pickle()``.

Added ``index_constructor``, ``columns_constructor`` to ``Frame.from_concat``.

Fixed issue in ``Frame.insert_after()``, ``Frame.insert_before()``, ``Series.insert_after()``, ``Series.insert_before()`` with negative ``ILoc`` labels.

Added ``Frame.from_npy_mmap``; removed ``memory_map`` option from ``Frame.from_npy``.

Performance enhancements to ``Frame.from_npy`` and ``Frame.from_npz``.

Added ``consolidate_blocks`` Boolean parameter to ``Frame.to_npz()`` and ``Frame.to_npy``.

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[]``.