Change the default docs theme and build

changelog.d/707.doc.rst

+Changed the default theme to sphinx_rtd_theme, and changed the sphinx configuration to go along with that. (gh pr #707)

docs/conf.py

@@ -106,7 +106,7 @@
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-html_theme = 'default'
+html_theme = 'sphinx_rtd_theme'
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the

docs/requirements-docs.txt

+Sphinx>=1.7.3,<2
+sphinx_rtd_theme>=0.3.0

tox.ini

@@ -53,7 +53,7 @@
 [testenv:docs]
 description = invoke sphinx-build to build the HTML docs, check that URIs are valid
 basepython = python3.6
-deps = sphinx >= 1.6.3, < 2
+deps = -r docs/requirements-docs.txt
        {[testenv]deps}
 commands = sphinx-build -d "{toxworkdir}/docs_doctree" docs "{toxworkdir}/docs_out" {posargs:-W --color -bhtml}
            sphinx-build -d "{toxworkdir}/docs_doctree" docs "{toxworkdir}/docs_out" {posargs:-W --color -blinkcheck}