Nonreactive callback for range.removed code

When a range is removed, if the component instance has a destroyed callback
defined, updateTemplateInstance is called and the destroyed callback is called
in the context of the updated templateInstance. updateTemplateInstance calls
getComonentData() which can create a reactive dependency. This doesn't seem
necessary since we're removing the range.

The problem surfaced in iron-router in combination with using the {{#each
helper. The each helper is currently the only builtin that adds a destroyed
callback. If a previous layout used {{#each and a new layout rendered, the
previous range would be removed in the new computation. Then, if we updated the
data context, the dep would change and the entire new layout would be rendered
again :-(.

cc @tmeasday.
Merge pull request #1904 from EventedMind/make-removed-nonreactive

Put range.removed code in a Deps.nonreactive callback