Set attribute instead of property.

Fix #3130.
Merge pull request #3131 from braddunbar/save-example

Set attribute instead of property.
vox example
Merge branch 'master' of https://github.com/jashkenas/backbone
Revert "Make new tests more thorough"

This reverts commit f814b85db65cae8715c67d33606b1352d1373f7f.

Revert "Return `id` assumption for simple polymorphic `Collection#model` factories."

This reverts commit 3f7fbdeec6cf39cb27ddce7e3e84586bfdee6be8.

Conflicts:
	test/collection.js

Revert "#2985 -- use 'change-id' as the event name"

This reverts commit 36e4925b9c1da95a9dd182718e3a4e33e15bd4eb.

Revert "Merge pull request #2985 from caseywebdev/generate-id"

This reverts commit 60b9cc1d186ad0496b317f8bf46d634d137f495b, reversing
changes made to 0c1838be63b19a064c70942b563bf6692d6b8a0d.

Conflicts:
	test/collection.js
Merge pull request #3132 from caseywebdev/generate-id-revert

Revert generateId