replace isotope (100KB) with salvattore (5KB) for feed layout (bug 1092331)

This is going to take some time (especially since I won't be able to resist untangling feed CSS)...Here's a couple hours in:

![screen shot 2014-11-10 at 2 39 57 pm](https://cloud.githubusercontent.com/assets/674727/4985169/847bf216-692a-11e4-8fa8-8d3a6902ee1b.png)

Salvattore is like a CSS-driven version of Masonry/Isotope. Much leaner at 5KB unmin.

I had to fork someone's fork of Salvattore that has balanced-height column support and I registered it to Bower as salvattore-moox.
Columns ```div```s are inserted by the library, and the ```li```s would be wrapped by the column ```div```s. And it'd be wrong to have ```div```s as children nodes of a ```ul```