Fix #110 Page not active in the navbar if output is not the default

Thanks to https://github.com/andreburgaud for investigating the issue
and submitting a patch.
Update release notes and thanks file
Add title for RSS icon in social widget
Change comments in _defaults. Use Label instead of heading
Remove pre style rules from elegant.css. Bootstrap and Pygments have them defined already
Fix Solarized Light Pygments theme. Make it easier to change Pygments theme

The style is also slightly changed