Pymemcache

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* Fix ``setup.py`` dependency on six already being installed.

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* Public classes and exceptions can now be imported from the top-level
``pymemcache`` package (e.g. ``pymemcache.Client``).
`197 <https://github.com/pinterest/pymemcache/pull/197>`_
* Add UNIX domain socket support and document server connection options.
`206 <https://github.com/pinterest/pymemcache/pull/206>`_
* Add support for the ``cache_memlimit`` command.
`211 <https://github.com/pinterest/pymemcache/pull/211>`_
* Commands key are now always sent in their original order.
`209 <https://github.com/pinterest/pymemcache/pull/209>`_

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* Change set_many and set_multi api return value. `179 <https://github.com/pinterest/pymemcache/pull/179>`_
* Fix support for newbytes from python-future. `187 <https://github.com/pinterest/pymemcache/pull/187>`_
* Add support for Python 3.7, and drop support for Python 3.3
* Properly batch Client.set_many() call. `182 <https://github.com/pinterest/pymemcache/pull/182>`_
* Improve _check_key() and _store_cmd() performance. `183 <https://github.com/pinterest/pymemcache/pull/183>`_
* Properly batch Client.delete_many() call. `184 <https://github.com/pinterest/pymemcache/pull/184>`_
* Add option to explicitly set pickle version used by serde. `190 <https://github.com/pinterest/pymemcache/pull/190>`_

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* pypy3 to travis test matrix
* full benchmarks in test
* fix flake8 issues
* Have mockmemcacheclient support non-ascii strings
* Switch from using pickle format 0 to the highest available version. See `156 <https://github.com/pinterest/pymemcache/pull/156>`_

*Warning*: different versions of python have different highest pickle versions: https://docs.python.org/3/library/pickle.html

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* Documentation improvements
* Fixed cachedump stats command, see `103 <https://github.com/pinterest/pymemcache/issues/103>`_
* Honor default_value in HashClient

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* Drop support for python 2.6, see `109 <https://github.com/pinterest/pymemcache/issues/139>`_