use v8 cache data for vm script
the var fileScript = new vm.Script(source, { filename: filePath }); does not need be redone every time, it doesn't hold context state. The thing we are caching this.sandbox actually does hold state.
@krisselden are you suggesting do it once when the Node server comes up only? We currently do it once on startup and everytime some calls reload.
It would make reload() cheaper, but for some reason I had it in my head we were doing a new one for different sessions.
Aah no we don't do it for different sessions but when the Node process starts up and reload. I'll put a PR that splits this so reload is cheaper.