Use a more recent version of Sphinx

Author: wouterj

.travis.yml

@@ -9,7 +9,7 @@ cache:
         - $HOME/.cache/pip
         - _build
 
-install: pip install sphinx==1.1.3
+install: pip install sphinx~=1.3
 
 script: sphinx-build -nW -b html -d _build/doctrees . _build/html