Second attempt at caching the attributes of a section of the outline. The goal is to handle an onslaught of hits to a single page that comes when a link gets tweeted. New strategies: 1. If there are more than 25 elements in the cache, delete the cache. Keep it from growing too big, keep from caching things that aren't accessed much (no point). 2. If we reference an item that was cached more than 3 minutes ago, delete it. Makes sure things get recalc'd periodically.