Release 1.14.3

The main change for this release is that the pthreads library is
not needed on any Windows build anymore. Thanks to Steven G. Johnson.
Also, the internal Zstd sources have been updated to 1.3.4; expect
an important performance boost (can be up to 10%, specially for low
compression levels).

For more info, please see the release notes in:

https://github.com/Blosc/c-blosc/blob/master/RELEASE_NOTES.rst