Porportional media queries (px to em breakpoints)

Porportional media queries:
- Scale text accordingly.
- Fixes issue with some site layouts so they don't get squeezed, overlapping etc. when zooming-in.

New breakpoints:
- 40em (replaces 568px/35.5em)
- 60em (replaces 978px/61.125em)
- 80em (replaces 1180px/73.750em)

Note:
- Instead of complex em values which is closer to the actual px-values​​, I chose to start with a simpler approach with 40-60-80em to begin designing with.