[DAEMON-6] appcd: Filesystem watcher

androidlib, ioslib, jdklib, and windowslib need a filesystem monitoring library that can be notified when a specific path changes. Node has a built-in fs.watch() function which works fine on Linux and Windows, but doesn't work well on OS X where it doesn't report the correct file path. This can be fixed by using the fsevents module. The chokidar module comes close to solving this need, but I discovered two blocking bugs: one with watching paths that do not exist and one with nested paths. It also currently has 39 open issues, some of which are a little scary sounding. Additionally, chokidar uses readdirp which apparently has performance issues due to all of the file stating.