Split out viz rendering into a function, in preparation for redrawing the viz around a new center node
Create NodeTree model, and migrate D3 format conversion there
Split out render_viz function, toward re-rending on node click
Increase weight of leaf node each time it is repeated
Add JQuery; minor tweaks
Simplify JSON generated from CSV, and improve "empty key equals self" system
Leaf nodes should be visible
Create shallower hashes by one level (can be grafted later in viz)