Update sphinx to 1.8.3

[pyup-bot]

This PR updates Sphinx from 1.8.2 to 1.8.3.

Changelog

1.8.3

==============================

Dependencies
------------

Incompatible changes
--------------------

Deprecated
----------

Features added
--------------

* LaTeX: it is possible to insert custom material to appear on back of title
page, see discussion of ``'maketitle'`` key of :confval:`latex_elements`
(``'manual'`` docclass only)

Bugs fixed
----------

* 5725: mathjax: Use CDN URL for "latest" version by default
* 5460: html search does not work with some 3rd party themes
* 5520: LaTeX, caption package incompatibility since Sphinx 1.6
* 5614: autodoc: incremental build is broken when builtin modules are imported
* 5627: qthelp: index.html missing in QtHelp
* 5659: linkcheck: crashes for a hyperlink containing multibyte character
* 5754: DOC: Fix some mistakes in :doc:`/latex`
* 5810: LaTeX: sphinxVerbatim requires explicit "hllines" set-up since 1.6.6
(refs: 1238)
* 5636: C++, fix parsing of floating point literals.
* 5496 (again): C++, fix assertion in partial builds with duplicates.
* 5724: quickstart: sphinx-quickstart fails when $LC_ALL is empty
* 1956: Default conf.py is not PEP8-compliant
* 5849: LaTeX: document class ``\maketitle`` is overwritten with no
possibility to use original meaning in place of Sphinx custom one
* 5834: apidoc: wrong help for ``--tocfile``
* 5800: todo: crashed if todo is defined in TextElement
* 5846: htmlhelp: convert hex escaping to decimal escaping in .hhc/.hhk files

Testing
--------

Links

• PyPI: https://pypi.org/project/sphinx
• Changelog: https://pyup.io/changelogs/sphinx/
• Homepage: http://sphinx-doc.org/

[pyup-bot]

Closing this in favor of #663