Replace Address with model.Document objects.

import.js
	-In `importOpenAddressesFile()`, replace the `addressCreator()`
	Transform stream with a `documentCreator` stream, which creates
	`pelias-model.Document` objects from raw CSV records.
	-As per a comment on pelias/addresses issue #3
	(https://github.com/pelias/addresses/issues/3#issuecomment-67219981),
	imports will probably migrate to using `Document` objects in the
	future.