Automatically manage binding state such that elements can be garbage collected normally.
 - when elements are inserted and removed normally, they will be cleaned up automatically.
 - when an element is not inserted into the dom, you must call cancelUnbindAll() on it for bindings to remain active and subsequently must call unbindAll to dispose of it.
 - WARNING: insertedCallback changed to inserted; removedCallback changed to removed; attributeChangedCallback changed to attributeChanged.