removed toobusy dependency & improved graceful shutdown

Fixes #723

- Use the hapi built in `maxEventLoopDelay` instead of toobusy
- Use `server.load` for memory stats instead of memory_monitor.js (lose heapTotal, but s'ok)
- Ensure all resources that keep the event loop alive are closed on shutdown
- updated mysql dependency
Cool.  We should file a follow-up bug to change the name of this config option to match.