Fully document all filters in the breadcrumbs class.
Remove usage of `empty`.
Remove `wpseo_breadcrumb_single_link_with_sep` filter as it's now, basically, stupid.
Add a check to prevent having an empty wrapper tag.
Document all filters and actions in frontend class
Removed a check for `is_wp_error` as this could never be true when `is_string` is true.
Improve documentation in class-breadcrumbs so it can be read out of context too
Introduce new GooglePlus class for output of G+ specific meta data
Add option to enable GooglePlus specific output
Move loading of the 3 different Social metadata classes to get_header to prevent notice for `is_singular` being called too early
Remove to do as, well, I've done it ;)
Fully document all filters in all frontend classes.
Refactor some filters in class-twitter.php to make them Twitter class specific.
Update banners and banner logic.
Remove unused `$options` and related functionality.
Clean up unused G+ code.