Added horizontal cards

Added new horizontal cards to render articles or shop items with an horizontal layout. 

Also I've added a new properties structure for card_horizontal component: 
properties[:data] -> where the data to render should came
properties[:options] -> where the modifiers for the card should came (classes, theme, color...etc...)

This is how it looks:
(the image on the right should come from backend in landscape, but now came as a square :confused: )
![screen shot 2014-08-12 at 11 39 31](https://cloud.githubusercontent.com/assets/1152640/3888808/a0fedd58-2204-11e4-8f67-a883538c90dd.png)
![screen shot 2014-08-12 at 11 53 01](https://cloud.githubusercontent.com/assets/1152640/3888929/81b4abce-2206-11e4-9694-a32cc0de1d9f.png)

I don't think colours should be specified within the base media object