Generates hierarchy.json
Adds rubric:ancestry rake task

`rubric:ancestry` takes data from `classify.yml` and generates `ancestry.json` — a JSON of direct_ancestry relations for each Ruby core class to be used by D3's edge bundling visualizations.
Generates ancestry.json
Adds edge_bundling.js
Adds CSS for edge bundling
Fixes misaligned links in diagram

Moves `text-align: center` rule out of `body` as it pushes the whole links diagram off to the right rather than being positioned correctly on the grid.