Fixed parameters for `change` event on computeds.

Took me some time to figure out why my code behaved so weird...

A `change` event gets (model, options) and `change:*` gets (model, value, options).
In its current state epoxy passes (model, value, options) to `change` as well.

Please note: I updated the code inside `modifyArray` and `modifyObject` as well,
even though I don't know what they do (they are not used at all).

"change" (model, options) — when a model's attributes have changed.
"change:[attribute]" (model, value, options) — when a specific attribute has been updated.

http://backbonejs.org/#Events-catalog