Update tox from 2.9.1 to 3.2.1

pyup-bot · pyup-bot · commit c1aa6f2e2219 · 2018-08-31T20:48:45.000-07:00
diff --git a/requirements_dev.txt b/requirements_dev.txt
@@ -3,7 +3,7 @@ bumpversion==0.5.3
 wheel==0.31.1
 watchdog==0.9.0
 flake8==3.5.0
-tox==2.9.1
+tox==3.2.1
 coverage==4.5.1
 Sphinx==1.7.1
 twine==1.10.0
