make the example config file valid json
don't use require relative in the example watcher
minor whitespace cleanup; remove require_relative
ignore jar file artifact
basic infrastructure for allowing watchers to stop cleanly

this is sufficient for the docker and dns watchers, which run in their
own loops
special stop handler for the zookeeper watcher

calling stop! should unsubscribe from pending events, but we handle this
manually anyway
ensure we explicitly stop all watchers in main thread
re-raise exceptions instead of `throw`ing 'em
Merge pull request #36 from airbnb/cleanup

Cleanup & Proper Exit Handling