Worked on SMN-28.

Topbar.js
- Relocated menu functions to the linking function instead of the controllers.
- Removed mobilecheck function; it's useless and counterproductive.
- Added whitespace for readability
- Added documentation
- Added analytics tracking
  - Added event for menu opening
  - Added event for menu closing
- Changed the location of the <nav>. It's now inside the topbar.
- Removed unnecessary HTML elements (container and wrapper) in the index.html.