pyup: Scheduled weekly dependency update for week 40 (readthedocs#31)

pyup:  Scheduled weekly dependency update for week 40

Author: humitos

docs/requirements.txt

@@ -1,7 +1,7 @@
 sphinx==1.8.5  # pyup: ignore
 sphinx-autoapi==1.1.0
 sphinx-rtd-theme==0.4.3
-sphinx-tabs==1.1.12
+sphinx-tabs==1.1.13
 sphinx-prompt==1.1.0
 sphinx-version-warning==1.1.2
 sphinx-notfound-page==0.4