Multisite Support

[glibersat]

Hi guys,

We are happily using this package on our app and we're going multisites in a few weeks and currently migrating our code.
I see that I have two options to do that:

• Change my model with a custom one using AbstractNotification
• Fork and add the support for the contrib.sites framework

If I'm going with the second option, would you guys be open for a PR?

Thank you,

Guillaume