Initial locations-promo layout

The initial layout includes:
* placeholder copy, awaiting final copy.
* BNB campus content
* BNB on locations index
* BNB page images

Changes to be committed:
modified:   _data/locations.yml
modified:   _includes/tertiary.html
new file:   _layouts/locations-promo.html
new file:   locations/_posts/0100-01-01-bnb.md
new file:   locations/assets/campus/bnb-bg.jpg
new file:   locations/assets/campus/bnb-bg@2x.jpg
modified:   locations/index.html
modified:   scss/pages/_locations.scss
modified:   stylesheets/app.css
Copy update for Serving YML
Merge locations-promo and master
Update locations-promo copy
Merge branch 'locations-promo'