Merge pull request #43 from aio-libs/pyup-update-pytest-3.0.7-to-3.1.0

Update pytest to 3.1.0

requirements-dev.txt

@@ -1,6 +1,6 @@
 -e .
 flake8==3.3.0
 ipdb==0.10.3
-pytest==3.0.7
+pytest==3.1.0
 pytest-asyncio==0.5.0
 pytest-cov==2.5.1