Update bleach to 3.1.2

[pyup-bot]

This PR updates bleach from 3.1.0 to 3.1.2.

Changelog

3.1.1

-----------------------------------

**Security fixes**

* ``bleach.clean`` behavior parsing ``noscript`` tags did not match
browser behavior.

Calls to ``bleach.clean`` allowing ``noscript`` and one or more of
the raw text tags (``title``, ``textarea``, ``script``, ``style``,
``noembed``, ``noframes``, ``iframe``, and ``xmp``) were vulnerable
to a mutation XSS.

This security issue was confirmed in Bleach versions v2.1.4, v3.0.2,
and v3.1.0. Earlier versions are probably affected too.

Anyone using Bleach <=v3.1.0 is highly encouraged to upgrade.

https://bugzilla.mozilla.org/show_bug.cgi?id=1615315

**Backwards incompatible changes**

None

**Features**

None

**Bug fixes**

None

Bleach changes
==============

Links

• PyPI: https://pypi.org/project/bleach
• Changelog: https://pyup.io/changelogs/bleach/
• Repo: https://github.com/mozilla/bleach
• Docs: https://pythonhosted.org/bleach/

[pyup-bot]

Closing this in favor of #140