Log Message:
py-zstandard: updated to 0.12.0

0.12.0:

Backwards Compatibility Notes
* Support for Python 3.4 has been dropped since Python 3.4 is no longer
  a supported Python version upstream. (But it will likely continue to
  work until Python 2.7 support is dropped and we port to Python 3.5+
  APIs.)

Bug Fixes
* Fix ``ZstdDecompressor.__init__`` on 64-bit big-endian systems.
* Fix memory leak in ``ZstdDecompressionReader.seek()``.

Changes
* CI transitioned to Azure Pipelines (from AppVeyor and Travis CI).
* Switched to ``pytest`` for running tests (from ``nose``).
* Bundled zstandard library upgraded from 1.3.8 to 1.4.3.