Path.py

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- 163: Corrected 'pymodules' typo in package declaration.

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- Minor packaging refresh.

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- 156: Re-wrote the handling of pattern matches for
``listdir``, ``walk``, and related methods, allowing
the pattern to be a more complex object. This approach
drastically simplifies the code and obviates the
``CaseInsensitivePattern`` and ``FastPath`` classes.
Now the main ``Path`` class should be as performant
as ``FastPath`` and case-insensitive matches can be
readily constructed using the new
``path.matchers.CaseInsensitive`` class.

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- 153: Skip intermittently failing performance test on
Python 2.

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- 130: Path.py now supports non-decodable filenames on
Linux and Python 2, leveraging the
`backports.os <https://pypi.org/project/backports.os>`_
package (as an optional dependency). Currently, only
``listdir`` is patched, but other ``os`` primitives may
be patched similarly in the ``patch_for_linux_python2``
function.

- 141: For merge_tree, instead of relying on the deprecated
distutils module, implement merge_tree explicitly. The
``update`` parameter is deprecated, instead superseded
by a ``copy_function`` parameter and an ``only_newer``
wrapper for any copy function.

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- 151: No longer use two techniques for splitting lines.
Instead, unconditionally rely on io.open for universal
newlines support and always use splitlines.