Coalesce Events

* Use a Notifier instead of ThreadedNotifier
* Use a timeout of 100ms
* On timeout, keep only the last event for each file
* Use defaultdict for future extensibility
PEP 8
GaretJax's comments
Merge the two classes together
Reduce the timeout
Merge pull request #9 from wichtounet/coalescing

Coalescing events from pyinotify