We need to scroll to the top of the page, when showing pages

By Default, the scroll position is preserved while transitioning routes. However, at times this isn't the desired behaviour.
We need to scroll to top for the following pages:

- [ ] Home
- [ ] All Courses
- [ ] My Courses
- [ ] Course Timeline (Course Overview)
- [ ] Course/:id

### How ?
Use [ember-router-scroll](https://github.com/dollarshaveclub/ember-router-scroll) plugin, and use the mixin at the mentioned routes.

Don't `window.scrollTop(0, 0)` in beforeModel or similar hook. This will not preserve scroll position when using browser's back button. #DontBreakTheWeb