Proper tracking of subfolders contents

[GianniCarlo]

Let's say that the Documents folder is being watched, and folder 1 is added with a subfolder 1 inside it.

• Documents
  • folder 1
    • subfolder 1

The watcher will correctly pick up the folder 1 addition, but if you add later a subfolder 2 inside folder 1, the watcher will not notify that folder 1 had an addition.

The current solution then, is not being exhaustive, it only detects changes at the surface level

[GianniCarlo]

A possible solution (although not sure how well it'll scale with n folders), is to add a watcher for each subfolder that is added

[GianniCarlo]

This should be solved by the addition of the DirectoryDeepWatcher class in da9f2c4 . Readme is updated with instructions on how to use it