rewrite instrument.js to use cpr

[msridhar]

We should rewrite instrument.js to use cpr instead of ncp. We are already stuck on some old ncp version due to API changes, and it also is preventing instrument.js from working on io.js (due to AvianFlu/ncp#79). Additionally, I'd like to add an option so that rather than writing the _orig_.js files, we simply point back to the original files, or put the original files in some parallel directory structure (but this will take some thought).