Add tox setup

setup.py

@@ -14,12 +14,16 @@ setup(name='config-spec',
       ],
       extras_require={
           'dev': [
-              'pylint',
               'autopep8',
               'pytest',
               'pytest-flake8',
               'pytest-cov',
-              'pytest-sugar'
+              'pytest-sugar',
+              'tox'
+          ],
+          'test': [
+              'pytest',
+              'pytest-flake8'
           ]
       },
       long_description=open('README.md').read(),

tox.ini

@@ -0,0 +1,6 @@
+[tox]
+envlist = py36, py37, py38
+
+[testenv]
+extras = test
+commands = pytest