Bug fixes and improvements.

1. Pull in @heyitsgarrett's updates, as seen on: http://heyitsgarrett.com/wethevisualization/issue.html?issue=Foreign%20Policy
2. Introduce some performance improvements by not relying on overall analysis of the initial collection of petitions.
3. Clean up some of the code.

Note that the page URL from any referrers should change from `issue.html` to `index.html`.