Use the medium weight on facia-cards

- Use the medium weight on facia-cards.
- Clean up mixin use in item-layouts
- Tweak item-gutters

![screen shot 2014-09-25 at 19 05 11](https://cloud.githubusercontent.com/assets/1607666/4409561/84c386c8-44de-11e4-83fe-d501b324a4a0.png)
Out of interest why do you want `6px` rather than a clean division of our `20px` gutter such as `5px`?