Use new `.breadcrumb-item` class instead of child selectors and `li` tag selectors,
so as to no longer require the usage of `<ol>`-based markup.
Rename variables to follow naming conventions:
* $breadcrumb-padding-vertical => $breadcrumb-padding-y
* $breadcrumb-padding-horizontal => $breadcrumb-padding-x
Introduce new variable: $breadcrumb-item-padding
[skip sauce]
- Simpler main nav on all pages
- Back to purple masthead on homepage instead of dark graphite
- Active link styles on the main nav
- Cleaned up sidebar nav
- New docs layout name
- Homepage copy edits
- Updated bright purple docs color
