Bump bleach from 2.1.3 to 3.1.1

Bumps [bleach](https://github.com/mozilla/bleach) from 2.1.3 to 3.1.1.
- [Release notes](https://github.com/mozilla/bleach/releases)
- [Changelog](https://github.com/mozilla/bleach/blob/master/CHANGES)
- [Commits](mozilla/bleach@v2.1.3...v3.1.1)

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

requirements.txt

@@ -3,7 +3,7 @@ appnope==0.1.0
 backports-abc==0.5
 backports.functools-lru-cache==1.5
 backports.shutil-get-terminal-size==1.0.0
-bleach==2.1.3
+bleach==3.1.1
 cachetools==0.8.0
 configparser==3.5.0
 ConnPlotter==0.7a0