The data-vocabulary.org schema is being deprecated.
We're now using the BreadcrumList data from the latest and greatest schema.org.
FIX: categories_breadcrumb helper to support more than 2 levels of categories.
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
- add microdata based on schema.org
- add breadcrumb on the top of topic
- add navigations link on the bottom of every pages
- add category description on the category list
