Document that exceptions inside a callback attached to a Deferred locks the deferred

[mikesherov]

It locks in the sense that no other callbacks will ever be called in the deferred, per @jaubourg

Please see http://bugs.jquery.com/ticket/11292 for more information

[dmethvin]

This was fixed in 3.0 but still needs to be documented for older versions. It affects a lot of Deferred methods so perhaps should be put in a central location, or at the very least made into a reusable thing.