Switch Sphinx theme to default (from alabaster)

The Alabaster theme looks nice and is certainly lightweight and simple,
but it lacks any means to get back to the TOC/index once you descend
into a topic page. Switch back to the default to keep the documentation
usable.

Author: bootc

docs/conf.py

@@ -113,7 +113,7 @@
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-html_theme = 'alabaster'
+html_theme = 'default'
 
 # 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