Document new behavior

Now when the service receives an error, the watcher stops releasing all resources, so if you try to stop the service after an error, you will get an exception.

README.md

@@ -118,3 +118,7 @@ nsfw.actions = {
 ## Installation
 NSFW is a native node module and requires Node-Gyp to be functional before you can install it.
 Make sure you have completed installing all of the dependencies listed for [Node-Gyp](https://github.com/nodejs/node-gyp) on your operating system.
+
+## Breaking changes
+Prior to version 2.3.0 when the service receive an error, the service is shutdown but the watcher is not stopped.
+Now when the service receives an error, the watcher stops releasing all resources, so if you try to stop the service after an error, you will get an exception.