#224 – Implements settings page design and deprecates some layout-specific CSS

- Removes docs.scss and app.scss specific CSS.
- Abstracts those styles to columns. There is probably room for more modularity here.
- Adds a new color.
- Updates markup in account settings and styleguide.

Note: I didn't abstract the subheadings in Settings to different views and pages. I only touched markup and CSS. We'll probably want to take things like "Invitations" and directions for running the app and organize them into different sections.