Add recipe for magit-filenotify.

This requires Emacs 24.4, which is not yet released.  Therefore I
omitted the `:minimum-emacs-version' property for now but it should be
activated when Emacs 24.4 is released.

Signed-off-by: Rüdiger Sonderfeld <ruediger@c-plusplus.de>
Merge pull request #1308 from ruediger/magit-filenotify

Add recipe for magit-filenotify.