Require cls-bluebird before installing the require hook for bluebird so client code can use cls-bluebird without conflicts (#152, thanks to @jonathansamines).
Fix tracing of https client calls in Node.js 8.9.0.
Add support for Node.js 12 (except for two optional features that rely on native addons which are not yet available for Node.js 12, CPU profiling and reporting uncaught exceptions).