Build on a modern version of Node

[taylor-sutton]

Right now building and testing requires Node 7. Tests seem to fail for some reason on Node 12, needs investigation.

[taylor-sutton]

Partial progress: https://github.com/Clever/wag/tree/wag-v8.0-node14
The circuit breaker stuff is tricky. Also, hystrixjs doesn't even have a live codebase any more, NPM links to a dead bitbucket page, it just exists in the NPM archives, so that's uh, not great.