Bump bleach from 2.0.0 to 3.1.4

Bumps [bleach](https://github.com/mozilla/bleach) from 2.0.0 to 3.1.4.
- [Release notes](https://github.com/mozilla/bleach/releases)
- [Changelog](https://github.com/mozilla/bleach/blob/master/CHANGES)
- [Commits](mozilla/bleach@v2.0...v3.1.4)

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -82,7 +82,7 @@ pygments==2.2.0
 humanize==0.5.1
 markdown>=2.6,<2.7
 pygal>=2.3,<2.4
-bleach==2.0.0
+bleach==3.1.4
 
 # Google logging
 gcloud==0.18.3