• Don't hard-code/expose CREATE_NO_WINDOW on Windows (I'll aggressively
  remove the global without a deprecation here), taking advantage of the
  fact that the subprocess module now exposes the constant on Windows.
• Clarify the documentation in the rcParams for ffmpeg_path and
  convert_path. 1) subprocess.Popen (which is really what we're using)
  is not exactly just searching in the $PATH -- see the big warning to
  that respect in the CPython docs. 2) One doesn't actually need to put
  an absolute path for convert on Windows -- Matplotlib now handles this
  transparently.

PR Summary

PR Checklist

Tests and Styling

• Has pytest style unit tests (andpytest passes).
• IsFlake 8 compliant (installflake8-docstrings and runflake8 --docstring-convention=all).

Documentation

• New features are documented, with examples if plot related.
• New features have an entry indoc/users/next_whats_new/ (follow instructions in README.rst there).
• API changes documented indoc/api/next_api_changes/ (follow instructions in README.rst there).
• Documentation is sphinx and numpydoc compliant (the docs shouldbuild without error).