serve: Fix corner cases where the pipeline doesn't run correctly. * When `chef serve` is run before the `assets` folder is created, monitor that folder suddenly appearing and rebuild the pipeline. * Do the same when the `config.yml` file has changed.

{
  "name": "PieCrust",
  "version": "0.0.1",
  "private": "true",
  "dependencies": {
    "bootstrap": "~3.3.2"
  }
}