Converts to less complex code and uses the (newer) AE::io style
Fixes error in documentation
Fixes KQueue backend bug which causes CPU usage to peg at 100%

- Adds EV_CLEAR to KQueue to avoid firing multiple times for each event
  (thanks to gdxhsw++ for the bug report and patch)
  https://github.com/gdxhsw/AnyEvent-Filesys-Notify

- Adds each subdirectory and file to the kqueue watch. This is not
  practical as you need to open a filehandle for each monitored path.
Updates the documentation and issue warnings for KQueue filehandles

- Highlights the shortcomings of using the KQueue backend
Preps for release