Merge pytest.ini with setup.cfg, remove doctest opt in setup.cfg

Got confused when I couldn't find doctest_optionflags in setup.cfg, but then found them in pytest.ini. Is there a reason pytest is configured in two places? I might have misunderstood the setup,
I also removed --doctest-modules from addopts since that's added to env on the linux travis job, and set by invoke test --doctest otherwise.

Author: tetov

pytest.ini

@@ -17,7 +17,7 @@ exclude =
 convention = numpy
 
 [tool:pytest]
-testpaths = tests
+testpaths = src tests
 norecursedirs =
     migrations
 
@@ -28,9 +28,9 @@ python_files =
 addopts =
     -ra
     --strict
-    --doctest-modules
     --doctest-glob=\*.rst
     --tb=short
+doctest_optionflags= NORMALIZE_WHITESPACE IGNORE_EXCEPTION_DETAIL ALLOW_UNICODE ALLOW_BYTES
 
 [isort]
 force_single_line = True