Update the dom in the DOMUI phase

[justinbmeyer]

currently, we listen to notify on observations. This is so we can immediately "teardown"
child bindings as done in this test: 42a191a#diff-f265d6a6b6b64d4d096fddcf7d620a76

This is fine ... but ideally, we'd should be able to make sure that updates only happen in the DOM UI phase. We can enqueue the actual change separate from the teardown.