Convert pagination template to BS3.

- pagination class is applied to ul, not wrapper div
- Page info element should be a span, not an anchor, since is not
meant to be clicked.
Convert right panel to BS3 in base.html.

Also remove excesive top margin in the first header of a panel.
Convert mezzanine.blog to BS3.

Includes blog post list, detail, filter panel and custom styles.
Remove excessive whitespace from mezzanine.css.
Convert ratings to BS3.