Code review comment for lp:~diegosarmentero/ubuntuone-client/darwin2-fsevents

Branch fixed.
I added the event codes in the filesystem_notifications/__init__.py so we can create where it actually does this os dependent thing, and we can grab it from anywhere, because implementing it as a class attribute was breaking a lot of things.

Also i remove the if sys.platform == "win32": import decorators
on common, and in the future branch, when i add the darwin part, i'll make os_helper import the proper decorator based on the platform as it should be.