Added silent option to model.destroy

I don't know if that is on purpose but `model.destroy` does not support `silent: true` option. I haven't been able to find a PR or issue about it so here's one.

I'd like to have this because some of my views are tightly tied to the `"destroy"` event and I would like to control precisely when the even is triggered.

Beside, it is more consistent with all the other actions on models..