simplify our own flake8 config

tox.ini

@@ -118,26 +118,8 @@ commands =
     {[testenv:build]commands}
     twine upload --skip-existing dist/*
 
-# Flake8 Configuration
 [flake8]
-# Ignore some flake8-docstrings errors
-# NOTE(sigmavirus24): While we're still using flake8 2.x, this ignore line
-# defaults to selecting all other errors so we do not need select=E,F,W,I,D
-# Once Flake8 3.0 is released and in a good state, we can use both and it will
-# work well \o/
-ignore = D203, W503, E203, N818
+extend-ignore = E203
 per-file-ignores =
     src/flake8/formatting/_windows_color.py: N806
-exclude =
-    .tox,
-    .git,
-    __pycache__,
-    docs/source/conf.py,
-    build,
-    dist,
-    tests/fixtures/*,
-    *.pyc,
-    *.egg-info,
-    .cache,
-    .eggs
 max-complexity = 10