Scheduled weekly dependency update for week 39 (#233)

* Update sphinx from 1.7.8 to 1.8.1

* Update aiohttp from 3.4.2 to 3.4.4

* Update pytest from 3.7.4 to 3.8.1

* Update pytest-cov from 2.5.1 to 2.6.0

* Update multidict from 4.3.1 to 4.4.2

Author: pyup.io bot

requirements-dev.txt

@@ -1,14 +1,14 @@
 attrs==18.2.0
 flake8==3.5.0
 coverage==4.5.1
-sphinx==1.7.8
+sphinx==1.8.1
 alabaster>=0.6.2
-aiohttp==3.4.2
+aiohttp==3.4.4
 jinja2==2.10
-pytest==3.7.4
-pytest-cov==2.5.1
+pytest==3.8.1
+pytest-cov==2.6.0
 yarl==1.2.6
-multidict==4.3.1
+multidict==4.4.2
 pytest-aiohttp==0.3.0
 pytest-sugar==0.9.1
 -e .