Update tox from 2.6.0 to 2.9.1

pyup-bot · pyup-bot · commit 74c7288edc0f · 2018-02-08T14:31:56.000+02:00
diff --git a/requirements.txt b/requirements.txt
@@ -11,5 +11,5 @@ pycodestyle==2.3.1
 pyflakes==1.6.0
 pyparsing==2.2.0
 six==1.11.0
-tox==2.6.0
+tox==2.9.1
 virtualenv==15.1.0
