Added widget section and flickr widget in styleguide

Say hello to our new "Widgets" section in the styleguide! 

The first one: Flickr widget. Uses image cards as main component to render the photos. 

![screen shot 2014-06-26 at 12 00 22](https://cloud.githubusercontent.com/assets/1152640/3397111/c5195044-fd18-11e3-9ca3-544d1979f6ba.png)

Are you sure you want to be including the `grid-wrapper--10` class on each of these? It would make more sense to me for the responsibility of the grid wrapper class to fall to file that loops over them all (as in Line 12 of your `app/views/styleguide/widgets/flickr-widget.html.haml` file below)

This is likely what's causing the extra space in the screenshot you attached.