Clean code with black and create setup.py.

setup.cfg

@@ -0,0 +1,20 @@
+[flake8]
+# Use black line length:
+max-line-length = 88
+extend-ignore =
+    # See https://github.com/PyCQA/pycodestyle/issues/373
+    E203,
+
+[mypy]
+warn_return_any = True
+warn_unused_configs = True
+namespace_packages = True
+
+[tox:tox]
+envlist = py36,py37,py38,py36-lint
+
+[testenv]
+deps =
+    pytest
+commands =
+    pytest tests