Remove the override for `Backbone.Model.change`, since it has been removed from Backbone. Partial fix for #244.
Insulate `super/subModel` tests better from each other using a model `scope` instead of `window`, to prevent test execution order from influencing the outcome.
Modify attributes directly, instead of calling `set`. Partial fix for #244.

This prevents Backbone 0.9.10's reworked changed/changedAttributes/previous machinery from being triggered more than once, thus setting incorrect changes.