Add a file watcher

[oubiwann]

It would help developers / contributors if they could have something the watches for project files and performs configured actions based on observed changes. There's probably a great way to do this in Erlang, and maybe already a tool for this in the ecosystem ... in which case we just need to take advantage of it :-)

Part of epic #102

[oubiwann]

Oh, nice: https://github.com/massemanet/inotify

[oubiwann]

Here's a rebar-ized and more updated fork: https://github.com/istr/erlinotify

[oubiwann]

The last one looks like it has had the most work done on it. It's still a bit out of date, though.

Forked it to: https://github.com/erlsci/inotify