Added tox configuration.

.gitignore

@@ -7,3 +7,6 @@ dist
 build
 _build
 distribute-*
+.tox/
+.vscode/
+venv/

tox.ini

@@ -0,0 +1,25 @@
+
+[tox]
+envlist = flake,package,py{36,37,38,39}
+skip_missing_interpreters = true
+
+[testenv]
+commands =
+    python setup.py test
+
+[testenv:flake8]
+skip_install = True
+deps =
+    flake8
+commands = flake8 {posargs}
+
+[testenv:package]
+skip_install = True
+deps =
+    check_manifest
+    wheel
+    twine
+commands =
+    check-manifest -v
+    python setup.py sdist bdist_wheel
+    python -m twine check dist/*