FIX(TEST): remove dirs from PYTEST addopts, so VSCode ...

can launch a single TC (microsoft/vscode-python#8849)

+ refact(build): mv pytest-ignores from
  setup.cfg --> conftest.py
+ doc(build): setup.cfg metadata sample explaining LIC-files
  for wheels & sdists.

Author: ankostis

MANIFEST.in

@@ -1,2 +1 @@
 include LICENSE CHANGES.rst
-

setup.cfg

@@ -1,5 +1,11 @@
 ## Python's setup.cfg for tool defaults:
 #
+[metadata]
+## Include CHANGES in wheel
+# `license_files` it affects only "wheels" (not "sdists"), and defaults to ~5 files,
+# see https://wheel.readthedocs.io/en/stable/user_guide.html#including-license-files-in-the-generated-wheel-file
+#license_files = CHANGES.rst LICENSE
+
 [bdist_wheel]
 universal = 1
 
@@ -9,16 +15,17 @@ universal = 1
 markers =
     slow: slow-running tests, run them: with: -m slow OR -m 'slow and not slow'
 
-# TODO: enable doctests in README.
-addopts         = graphtik/ test/ docs/source/ README.rst
+addopts =
+    --doctest-modules
     # Faciltate developer, rum'em all with -m 'slow or not slow'.
     -m 'not slow'
-    # Version-from-sources code in docs/conf/py fails due to different cwd.
+    # See https://stackoverflow.com/questions/42919871/avoid-no-commands-on-setup-py-with-py-test
+    --ignore=setup.py
+    # Version-from-sources trick fails due to different cwd.
     --ignore=docs/source/conf.py
     --doctest-report ndiff
     --doctest-continue-on-failure
     # --doctest-ignore-import-errors
-    --doctest-modules
     --doctest-glob=*.md
     --doctest-glob=*.rst
     --cov-fail-under=80