Refactor handleUserArgs() into a testable function.
Refactor handleUserArgs() into a testable function.

import.js
	-Rewrite `handleUserArgs()` such that it returns an object
	containing the interpreted results of an arguments array,
	instead of effectively taking over the script for the remainder
	of its duration by kicking off the import on its own. This'll
	allow us to test it.

pelias/openaddresses,pelias/openaddresses