Scheduled monthly dependency update for October (#271)

* Update sphinx from 1.7.8 to 1.8.1

* Update mypy from 0.620 to 0.630

* Update pytest-cov from 2.5.1 to 2.6.0

* Update pytest-isort from 0.2.0 to 0.2.1

docs/requirements.txt

@@ -1,4 +1,4 @@
 docutils==0.14
 Pygments==2.2.0
-Sphinx==1.7.8
+Sphinx==1.8.1
 sphinxcontrib-websupport==1.1.0

tests/requirements.txt

@@ -2,11 +2,11 @@ attrs==18.2.0
 coverage==4.5.1
 flake8==3.5.0
 isort==4.3.4
-mypy==0.620
+mypy==0.630
 pycodestyle==2.3.1  # pyup: ignore
 pyflakes==2.0.0
 pytest==3.8.1
-pytest-cov==2.5.1
-pytest-isort==0.2.0
+pytest-cov==2.6.0
+pytest-isort==0.2.1
 pytest-mock==1.10.0
 pytest-sugar==0.9.1