build: Clean up MANIFEST.in

[jpmckinney]

• List explicit files in docs, to avoid prune instruction
• Remove NEWS, which just points to docs/news.rst
• Remove README.rst, which is included by default
• Remove docs/make.bat, as docs are not built on Windows
• Remove self-reference to MANIFEST.in

[codecov[bot]]

Codecov Report

Merging #441 (5cdc0d1) into master (228b67d) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #441   +/-   ##
=======================================
  Coverage   80.36%   80.36%           
=======================================
  Files          23       23           
  Lines        1044     1044           
=======================================
  Hits          839      839           
  Misses        205      205           

Flag	Coverage Δ
unittests	80.36% <ø> (ø)

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