Fix «request», «sync» and «error» events documentation.

* signatures had wrong number of parameters;
* it was not documented that «error» is fired by fetch, sync and destroy methods. There are unit tests for this behavior in Backbone repo. 

I named first parameter using_underscores because modelOrCollection is quite unreadable IMHO, and Backbone docs already uses similar names (e.g. `this.model.get("viewer_url")`). Another option was to call it 'object' and write "first argument is a model or a collection", but it is quite verbose and require reader to read events' descriptions carefully to check if they are same or not.