Update sphinx from 1.5.5 to 1.6.3

Author: pyup-bot

{{cookiecutter.project_slug}}/requirements.txt

@@ -43,7 +43,7 @@ selenium==3.3.1
 simplejson==3.11.1
 six==1.10.0
 snowballstemmer==1.2.1
-Sphinx==1.5.5
+Sphinx==1.6.3
 sphinx-rtd-theme==0.2.4
 splinter==0.7.5
 tox==2.7.0