Simulate file watch

[Baptouuuu]

This will require #2.

Since watching is done as an uninterrupted loop, the events that will trigger the callback needs to happen concurrently. This means that in order to implement this the execution model of this package needs to switch to Fibers.

This will need some study to make sure inmind/async can even be used, and it will most likely need some refactoring of innmind/foundation to support async composition.