Update sphinx to 1.6.6

[pyup-bot]

There's a new version of sphinx available.
You are currently using 1.6.5. I have updated it to 1.6.6

These links might come in handy: PyPI | Changelog | Homepage

Changelog

1.6.6

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

Features added

• 4181: autodoc: Sort dictionary keys when possible
• VerbatimHighlightColor is a new
  :ref:LaTeX 'sphinxsetup' <latexsphinxsetup> key (refs: 4285)
• Easier customizability of LaTeX macros involved in rendering of code-blocks
• Show traceback if conf.py raises an exception (refs: 4369)
• Add :confval:smartquotes to disable smart quotes through conf.py
  (refs: 3967)
• Add :confval:smartquotes_action and :confval:smartquotes_excludes
  (refs: 4142, 4357)

Bugs fixed

• 4334: sphinx-apidoc: Don't generate references to non-existing files in TOC
• 4206: latex: reST label between paragraphs loses paragraph break
• 4231: html: Apply fixFirefoxAnchorBug only under Firefox
• 4221: napoleon depends on autodoc, but users need to load it manually
• 2298: automodule fails to document a class attribute
• 4099: C++: properly link class reference to class from inside constructor
• 4267: PDF build broken by Unicode U+2116 NUMERO SIGN character
• 4249: PDF output: Pygments error highlighting increases line spacing in
  code blocks
• 1238: Support :emphasize-lines: in PDF output
• 4279: Sphinx crashes with pickling error when run with multiple processes and
  remote image
• 1421: Respect the quiet flag in sphinx-quickstart
• 4281: Race conditions when creating output directory
• 4315: For PDF 'howto' documents, latex_toplevel_sectioning='part' generates
  \chapter commands
• 4214: Two todolist directives break sphinx-1.6.5
• Fix links to external option docs with intersphinx (refs: 3769)
• 4091: Private members not documented without :undoc-members:

Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.

Happy merging! 🤖