First cut of a function run container for NodeJS. So far, just the
simplest stuff: loads a user function and routes requests to it. The
user function is assumed to be in a file at a provided location. The
fission runtime is expected to place the file there securely (exactly
how we'll do that is TBD).
Doesn't handle path template params, query strings, etc. Will also
need to be extended later with some sort of hook for graceful
shutdown.