Fix in BaseView::getAttributes()

* Allow custom model::idAttribute
* Don't explode if model::id is undefined
Release 0.4.4.

* In BaseView::getAttributes(), call toString() on model.id, for better support of Mongoose.
* In BaseView::getAttributes(), support custom this.model.idAttribute.
* Remove reference to `global.isServer` in BaseView; easier to standalone test.
* Default `replace: false` in ClientRouter::redirectTo().
update HISTORY