feat: add configuration for tox (#36)

MANIFEST.in

@@ -2,3 +2,6 @@ global-include *.pyx *.pxd
 recursive-include tests *.py *.ttf LICENSE.txt
 recursive-include docs *.rst *.py make* _*/*
 prune docs/_build
+include *.md
+include *.txt
+include .coveragerc

tox.ini

@@ -0,0 +1,30 @@
+# 'Tox' is a tool for automating sdist/build/test cycles against
+# multiple Python versions:
+#   https://pypi.python.org/pypi/tox
+#   https://tox.readthedocs.io/
+
+# To run against a specific subset of Python versions, use:
+#   tox -e py37
+
+# Tox assumes that you have appropriate Python interpreters already
+# installed and that they can be run as (e.g.) 'python3.8'
+
+[tox]
+envlist =
+    lint
+    py36,py37,py38,py39,
+
+[testenv]
+deps= -Ur{toxinidir}/requirements-dev.txt
+passenv= PKG_CONFIG_PATH
+commands=
+    {envpython} setup.py build_ext -i --coverage
+    python -m pytest
+
+[testenv:lint]
+commands =
+    pre-commit run --all-files --show-diff-on-failure
+deps =
+    pre-commit
+skip_install = true
+passenv = PRE_COMMIT_COLOR