Update pytest from 3.6.2 to 3.6.3 (#116)

Author: pyup-bot

dev-requirements.txt

@@ -1,5 +1,5 @@
 -r requirements.txt
-pytest==3.6.2
+pytest==3.6.3
 pytest-asyncio==0.8.0
 pytest-aiohttp==0.3.0
 requests-mock==1.5.0