DO NOT MERGE.  Attempt to move instrumentation over to Istanbul.

A baby-step heading towards integrating Istanbul as envisioned by Tomaz.  The mapping from jscoverage to Istanbul is far from perfect, as this early work already demonstrates.  Maybe there's a better way?

I'm an advocate of using istanbul in its native way, but that idea has already been dismissed as impractical or incompatible with existing whiskey users.