Recursivly watches specified path and procuces events if file was created or modified.
Have two backends, one based on inotifywait port, another is erlang-native. If inotifywait
is not available (not in search path), then native naive backend is used automatically.
Scans directory structure periodically (10 seconds default), and compares with stored one,
and produces events (create and modify) if there are differences.
Relies on inotifywait binary and on shell trick to kill spawned binary, as inotifywait doesn't
read STDIN and therefore doesn't die on SIGPIPE signal if spawned process terminates.
1. Add more backends (Mac, Win)