Cross-platform efficient monitoring for changed files

[nrdvana]

The project currently has optional support for Linux::Inotify2, but if that isn't available it falls back to just checking mtime on each page load. I would like to have an event-driven filesystem watcher that works on all major platforms, but can fall back to a timer poll if needed.

It should be built on the Mojo IOLoop event system. This behavior should be wrapped in a separate module (and probably already exists on CPAN)