Pymemcache

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* Add TLS support for TCP sockets.
* Fix corner case when dead hashed server comes back alive.

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* Make MockMemcacheClient more consistent with the real client.
* Pass ``encoding`` from HashClient to its pooled clients when ``use_pooling``
is enabled.

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* The serialization API has been reworked. Instead of consuming a serializer
and deserializer as separate arguments, client objects now expect an argument
``serde`` to be an object which implements ``serialize`` and ``deserialize``
as methods. (``serialize`` and ``deserialize`` are still supported but
considered deprecated.)
* Validate integer inputs for ``expire``, ``delay``, ``incr``, ``decr``, and
``memlimit`` -- non-integer values now raise ``MemcacheIllegalInputError``
* Validate inputs for ``cas`` -- values which are not integers or strings of
0-9 now raise ``MemcacheIllegalInputError``
* Add ``prepend`` and ``append`` support to ``MockMemcacheClient``.
* Add the ``touch`` method to ``HashClient``.
* Added official support for Python 3.8.

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* Fix ``long_description`` string in Python packaging.

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* Fix ``flags`` when setting multiple differently-typed values at once.

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* Drop official support for Python 3.4.
* Use ``setup.cfg`` metadata instead ``setup.py`` config to generate package.
* Add ``default_noreply`` parameter to ``HashClient``.
* Add ``encoding`` parameter to ``Client`` constructors (defaults to ``ascii``).
* Add ``flags`` parameter to write operation methods.
* Handle unicode key values in ``MockMemcacheClient`` correctly.
* Improve ASCII encoding failure exception.