Update tox from 3.1.3 to 3.2.1

pyup-bot · pyup-bot · commit 1ffb91c0a1a2 · 2018-08-11T00:35:53.000+08:00
diff --git a/requirements_dev.txt b/requirements_dev.txt
@@ -14,7 +14,7 @@ quart==0.6.5;python_version>="3.6"
 # tests
 coverage==4.5.1
 flake8==3.5.0
-tox==3.1.3
+tox==3.2.1
 pytest==3.6.4
 pytest-runner==4.2
 pytest-asyncio==0.9.0
