Bump sphinx to 1.8.1

Author: JulienPalard

requirements.txt

@@ -1,21 +1,21 @@
-alabaster==0.7.10
+alabaster==0.7.12
 Babel==2.6.0
 blurb==1.0.7
-certifi==2018.4.16
+certifi==2018.8.24
 chardet==3.0.4
 docutils==0.14
 idna==2.7
-imagesize==1.0.0
+imagesize==1.1.0
 Jinja2==2.10
 MarkupSafe==1.0
-packaging==17.1
+packaging==18.0
 Pygments==2.2.0
-pyparsing==2.2.0
+pyparsing==2.2.2
 python-docs-theme==2018.2
-pytz==2018.4
+pytz==2018.5
 requests==2.19.1
 six==1.11.0
 snowballstemmer==1.2.1
-Sphinx==1.7.6
+Sphinx==1.8.1
 sphinxcontrib-websupport==1.1.0
 urllib3==1.23