Article breakpoint refactor

This is a far from perfect refactor but will still help making changes more easily. ie Getting rid of `!important` declarations would require deeper changes that would not actually help with maintainability in the short-medium term.

- Use media query abstraction in places we used standard $device variables
- Move `monocolumn-wrapper` as a global layout element

![Closing…](http://i.imgur.com/pRJfgXW.gif)