Single file support for inotify

[Yuhta]

Fix #16

[passcod]

Great work! Is inotify the only one that needs this, or do the others (polling) also need patching up?

Add yourself to the authors array in the Cargo.toml :)

@maurizi Not sure if your work on the Windows implementation supports single file watching, is it possible, harder, easy ? Just to let you know we're apparently going to support that now.

[Yuhta]

Patched and added PollWatcher; I don't have the environment to test FsEventWatcher but some one else can easily add it.

[maurizi]

@passcod Windows only really has a notion of watching directories, so this will be harder on Windows, since we'll have to add a layer above this that filters out events not for that file. Since it looks like PollWatcher will need that as well, it might be a good idea to implement it generically.

[passcod]

I'm going to merge this to fix #16. FS watchers in general seem to only support watching folders, with exceptions.

So we'll have to figure an internal API, perhaps with traits, so a backend could:

• implement a FileWatcher to watch individual files, so we'd have to recurse to watch everything, or
• implement a DirWatcher to watch individual folders, so we'd have to recurse to watch subfolders, or
• implement a RecursiveDirWatcher to watch everything, or
• any combination of the above

and then Notify itself would take care of wrangling each backend to provide the same public API.