add tox.ini file

.gitignore

@@ -5,4 +5,5 @@ __pycache__
 .DS_Store
 .vscode/
 build/
-dist/
+dist/
+.tox/

tox.ini

@@ -0,0 +1,29 @@
+# To use tox, see https://tox.readthedocs.io
+# Simply pip or conda install tox
+# If you use conda, you may also want to install tox-conda
+# then run `tox` or `tox -- {pytest args}`
+# To run in parallel using `tox -p` (this does not appear to work for this repo)
+
+# To rebuild the tox environment, for example when dependencies change, use
+# `tox -r`
+
+[tox]
+envlist = py{36,37,38}
+skip_missing_interpreters = true
+
+[testenv]
+recreate = false
+
+[testenv:py{36,37,38}]
+extras = testing
+deps =
+	sphinx2: sphinx>=2,<3
+	sphinx3: sphinx>=3,<4
+commands = pytest {posargs}
+
+[testenv:docs-{update,clean}]
+extras = rtd
+whitelist_externals = rm
+commands =
+	clean: rm -rf docs/build
+	sphinx-build {posargs} -b html docs/source docs/build/html