Keeping 13% of the points seems like a good balance.

bounds: -73.50796377699987 41.23795553600036 -69.9280530069999
42.88676061800015 (spherical)
pre-quantization: 0.398m (0.00000358°) 0.183m (0.00000165°)
topology: 85 arcs, 10733 points
simplification: retained 1353 / 10733 points (13%)
prune: retained 65 / 85 arcs (76%)
Add some style.  Also, refactor some:

  * Define more variables outside of callback, ala "Let's make a map"
    step-4.html (http://bost.ocks.org/mike/map/step-4.html)
  * Zoom in closer on MA.
  * Add target to pretty print json.