v0.3.0

* `DomainMiddleware` class renamed to `GracefulExpress`
* All public APIs throw on incorrect parameters
* `Graceful` is resilient to errors thrown by provided 'check' functions or registered 'shutdown' event handlers
* New mode in `GracefulExpress`: `inProcessTest`. If `true`, will not set up a domain for each request, allowing for easier in-process testing with `supertest`.
* `GracefulExpress`: tightens up graceful shutdown by:
  * Closing keepalive connections for all in-progress requests and idle sockets
  * Starting a socket reaper to continually look for and close idle sockets
  * Installing a backstop in case issues get through, return `Error` with `statusCode = 503`
* Logging: reduce verbosity, move to `thehelp-log-shim` to leave logging decisions to the process
* Upgrade to `1.x` series of `thehelp-last-ditch`, which doesn't send SMS by default any longer
* Substantial test coverage added
* Remove peer dependencies in favor of real dependencies
* Remove dependency on `lodash`