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

This is going to take some time...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.