I just wanted to notify you that I'm in the process of a semver-major release of the istanbul libraries. They are currently published to npm under the next tag but will likely be promoted to latest soon. The breaking changes include:

• dropping of node.js 6 (8.9.0 is the oldest officially support version)
• some API changes (some functions are now async, changes to reporting)

I don't have time right now to create a PR for this but if you do I can try giving pointers if you run into issues (feel free to tag me in any PR).