Release 2.15.1

Changes from 2.15.0 to 2.15.1

• Do not pass -m flags when compiling shuffle.c. This prevents the
  compiler from incidentally optimizing the code called independently
  of the runtime CPU check to these instruction sets, effectively
  causing SIGILL on other CPUs. Fixes #621. Thanks to @t20100 and @mgorny.

• Internal LZ4 sources bumped to 1.10.0.

• Allow direct loading of plugins by name, without relying on
  the presence of python. Thanks to @boxerab.

• Add b2nd_nans method (PR #624). Thanks to @waynegm.