Scheduled weekly dependency update for week 16 (#266)

* Update sphinx from 1.7.2 to 1.7.3

* Update pytest-mock from 1.8.0 to 1.9.0

* Update aiohttp from 3.1.2 to 3.1.3

Author: pyup.io bot

requirements-dev.txt

@@ -1,6 +1,6 @@
 attrs==17.4.0
 flake8==3.5.0
-sphinx==1.7.2
+sphinx==1.7.3
 pep257==0.7.0
 -e .
 aioredis==1.1.0
@@ -10,9 +10,9 @@ pynacl==1.2.1
 pytest==3.5.0
 pytest-aiohttp==0.3.0
 pytest-cov==2.5.1
-pytest-mock==1.8.0
+pytest-mock==1.9.0
 pytest-sugar==0.9.1
-aiohttp==3.1.2
+aiohttp==3.1.3
 multidict==4.1.0
 chardet==3.0.4
 yarl==1.1.1