Scheduled weekly dependency update for week 48 (#238)

* Update aiohttp from 2.3.2 to 2.3.3

* Update yarl from 0.14.0 to 0.15.0

Author: pyup.io bot

requirements-dev.txt

@@ -10,8 +10,8 @@ pynacl==1.2.0
 pytest-aiohttp==0.1.3
 pytest-cov==2.5.1
 pytest-mock==1.6.3
-aiohttp==2.3.2
+aiohttp==2.3.3
 multidict==3.3.2
 chardet==3.0.4
-yarl==0.14.0
+yarl==0.15.0
 aiomcache==0.5.2