Istanbul instrumenter library.
Version 1.1.x now implements instrumentation using Babel. The implementation is inspired
by prior art by @dtinth as demonstrated in the __coverage__ babel plugin.
It provides 2 "modes" of instrumentation.
The old API that is mostly unchanged (except for incompatibilities noted) and
performs the instrumentation using babel as a library.
A programVisitor function for the Babel AST that can be used by a Babel plugin
to emit instrumentation for ES6 code directly without any source map
processing. This is the preferred path for babel users. The Babel plugin is
called babel-plugin-istanbul.
Incompatibilities and changes to instrumentation behavior can be found in
v0-changes.md.
