New cards

- New card design
- Flexible by default
- Far more simple than existing cards
- New styles are hidden behind a feature flag

![screen shot 2014-08-13 at 15 15 29](https://cloud.githubusercontent.com/assets/271645/3906592/7ba864de-22f4-11e4-8bd1-985d1426a32d.png)
![screen shot 2014-08-13 at 15 15 45](https://cloud.githubusercontent.com/assets/271645/3906590/7ba60f18-22f4-11e4-81b8-075420a861d1.png)
![screen shot 2014-08-13 at 15 15 57](https://cloud.githubusercontent.com/assets/271645/3906591/7ba81ad8-22f4-11e4-908b-127403571467.png)
![screen shot 2014-08-13 at 15 16 09](https://cloud.githubusercontent.com/assets/271645/3906593/7ba91154-22f4-11e4-87bc-83a3b0dd4d41.png)
![screen shot 2014-08-13 at 15 16 20](https://cloud.githubusercontent.com/assets/271645/3906594/7baa4ea2-22f4-11e4-9e51-a829c0454bf0.png)
![screen shot 2014-08-13 at 15 16 28](https://cloud.githubusercontent.com/assets/271645/3906595/7bb8fab0-22f4-11e4-8799-5a9bcafec2c0.png)


To see the cards checkout this branch and flip the `cards_version` setting in the application config to `v2`.
Not something particular to this PR but there are quite a lot of `is-` prefixed classes throughout rizzo which are scoped to sections. Many of them do the same thing. Could we just define more, or use the current, utility classes for this? It needs an overall cleanup but there is already `is-faded-out` which has the same property as here: http://rizzo.lonelyplanet.com/styleguide/css-utilities/utility-classes

Not a great classname :/ Although equally is-invisible would make me assume it was using visibility: hidden