function fromArgv (baseDir, argv) {
	const pkgJson = parseArgv(argv)
	return ScalarObservable.create(pkgJson)
}
create an instance by parsing the explicit dependencies supplied via
command line arguments.
@param  {String} baseDir - base directory of the project.
@param  {Array} argv - command line arguments.
@return {Observabel} - an observable sequence of an `EntryDep`.