divisors returns empty list for 0
divisors returns empty list for 0

This is mainly for consistency with other words
(factors, group-factors, unique-factors)

mcandre/factor,mcandre/factor,kingcons/factor,erg/factor,erg/factor,erg/factor,kingcons/factor,kingcons/factor,erg/factor,kingcons/factor,erg/factor,erg/factor,mcandre/factor,mcandre/factor,mcandre/factor,erg/factor,mcandre/factor,mcandre/factor