[FileSystem] Added watcher.js.
[FileSystem] Added watcher-argv.js.
[FileSystem] Added watcher-spawn.js.
[FileSystem] Added watcher-spawn-parse.js.
[FileSystem] Added read-simple.js.
[FileSystem] Added write-simple.js.
[FileSystem] Added cat.js.
[FileSystem] Added read-stream.js.
Renamed chapter-2 to file-system.