Front-end update - Users page redesign

> No Pivotal Story

* Redesign of pages related to `User` model (`show`, `index` and `edit`)
* Fixed bug with navbar responsive layout
* Moved `edit` page javascript to pre-compiled javascript files rather than in-line scripts

See a live version [here](https://websiteone-bryan.herokuapp.com/users)

Pairing partners: @PeteBoucher