Change linting tox env to use pre-commit checks

Author: nicoddemus

tox.ini

@@ -15,10 +15,6 @@ commands =
 [testenv:linting]
 skipsdist = True
 usedevelop = True
-deps =
-    pytest-flakes
-    restructuredtext_lint
-    pygments
-commands =
-    pytest --flakes pytest_mock.py test_pytest_mock.py -m flakes
-    rst-lint CHANGELOG.rst README.rst
+extras = dev
+basepython = python3.6
+commands = pre-commit run --all-files --show-diff-on-failure