Update tox from 2.7.0 to 2.8.2

Author: pyup-bot

{{cookiecutter.project_slug}}/requirements.txt

@@ -46,7 +46,7 @@ snowballstemmer==1.2.1
 Sphinx==1.6.3
 sphinx-rtd-theme==0.2.4
 splinter==0.7.5
-tox==2.7.0
+tox==2.8.2
 translationstring==1.3
 virtualenv==15.1.0
 zope.component==4.3.0