Merge pull request #219 from tony/pyup-update-sphinx-1.5.2-to-1.5.3

Update sphinx to 1.5.3

Author: tony

requirements/doc.txt

@@ -1,7 +1,7 @@
 -r ./base.txt
 docutils==0.13.1
 requests[security]==2.13.0
-sphinx==1.5.2
+sphinx==1.5.3
 reportlab==3.3.0
 alabaster==0.7.9
 releases==1.3.0 # Updated from 1.2.0