Update tox from 2.7.0 to 2.8.1 (#376)

pyup.io bot · jettify · commit 7db36f4341d4 · 2017-09-06T23:33:07.000+03:00
diff --git a/requirements.txt b/requirements.txt
@@ -5,7 +5,7 @@ ipython==6.1.0
 flake8==3.4.1
 -e .[sa]
 sphinx==1.6.3
-tox==2.7.0
+tox==2.8.1
 pytest==3.2.1
 pytest-cov==2.5.1
 pytest-sugar==0.9.0
