Add support for tox to test across python versions

.gitignore

@@ -21,3 +21,4 @@ wheels/
 .installed.cfg
 *.egg
 MANIFEST
+.tox/

pyproject.toml

@@ -0,0 +1,5 @@
+[build-system]
+# These are the assumed default build requirements from pip:
+# https://pip.pypa.io/en/stable/reference/pip/#pep-517-and-518-support
+requires = ["setuptools>=40.8.0", "wheel"]
+build-backend = "setuptools.build_meta"

setup.py

@@ -30,7 +30,14 @@
       },
       extras_require={
           'dev': [
+              'flake8',
               'pytest',
+              'tox',
+              'wheel',
+              'setuptools',
           ],
+        'test': [
+            'coverage',
+        ],
     },
 )

tox.ini

@@ -0,0 +1,27 @@
+[tox]
+envlist = py{35,36,37}
+skip_missing_interpreters = True
+
+# Define the minimal tox version required to run;
+# if the host tox is less than this the tool with create an environment and
+# provision it with a tox that satisfies it under provision_tox_env.
+# At least this version is needed for PEP 517/518 support.
+minversion = 3.3.0
+
+# Activate isolated build environment. tox will use a virtual environment
+# to build a source distribution from the source tree. For build tools and
+# arguments use the pyproject.toml file as specified in PEP-517 and PEP-518.
+isolated_build = true
+
+[testenv]
+deps =
+    flake8
+    pytest
+commands =
+    python setup.py check -m -s
+    # flake8 .
+    py.test tests {posargs}
+
+[flake8]
+exclude = .tox,*.egg,build,data
+select = E,W,F