Added new competition card

This card will be used in the flickr widget.  

Some notes:
- I had to use certain things in the css to override the styles of card__content and card__hero... don't know if this is the best way to do that. (like https://github.com/lonelyplanet/rizzo/compare/jesus;competition_card?expand=1#diff-ce378de23680223984d33979732c6e39R360)
- The data structure in the stubs.. I made it up, so may be we have to change it..

I've added the three sizes in the styleguide. They look like this:

![competition_card](https://cloud.githubusercontent.com/assets/1152640/3369191/d6f6fe0c-fb7d-11e3-8deb-c907bf5f4acb.gif)