New node sentry prefers some node.js "preload" nonsense. I use this
"hack" to avoid having to make a lock-step change to the runner: tested
locally and then deployed to staging and tested there with both
server-side and client-side errors.
This PR refactors some common utilities out of lib/ and into shared/ and
eliminates some use of underscore.js, as well as general type
improvements done along the way.
