Improve visual design of documentation navigation

* Remove `border` from documentation navigation
* Add `margin` below `global-nav` so it's modular and in `content-container`
* Add margin to hero content in lieu of margin from global nav
* Add waypoints sticky to project
* Rename global nav JS elements for better clarity
* Use Waypoints to properly display docs navigation

https://trello.com/c/KNHdE47Q