Scss lint

Don't merge just yet

This adds an scss-lint config so we can lint our scss. It also has changes to article.scss in oasis to demonstrate a linted file. 

Still to do: 
- [x] Determine if we want 3 or 4 levels of specificity
- [x] Look further into usage of placeholders. Not sure if we are even using these, and if not we should probably start!