function unlinkCmd (cwd, argv) {
	const names = argv._.slice(1)

	return names.length
		? ArrayObservable.create(names)
			::mergeMap((name) => unlinkFromGlobal(cwd, name))
		: unlinkToGlobal(cwd)
}
unlink one or more previously linked dependencies. can be invoked via
`ied unlink`. E.g. `ied unlink browserify tap webpack` would unlink all
_three_ dependencies.
@param  {String} cwd - current working directory.
@param  {Object} argv - parsed command line arguments.
@return {Observable} - observable sequence.