bem'ing up the item
Merge branch 'material-sprint' of https://github.com/google/web-starter-kit into material-sprint

* 'material-sprint' of https://github.com/google/web-starter-kit:
  Renaming navigation classes as per @csswizardry review
  Cleaning up layout SCSS - Make sure as much as possible is behind optional classes - Rename everything to follow style convention - Add new class for JS binding - Rearrange SCSS to take advantage of nesting with &