Merge pull request #30 from mohankishore/pyup-update-sphinx-1.8.0-to-1.8.1

Update sphinx to 1.8.1

Author: mohankishore

requirements_dev.txt

@@ -5,7 +5,7 @@ watchdog==0.9.0
 flake8==3.5.0
 tox==3.4.0
 coverage==4.5.1
-Sphinx==1.8.0
+Sphinx==1.8.1
 twine==1.11.0
 sphinx_rtd_theme==0.4.1
 pytest==3.9.3