I am replacing the http:// in x if exists because SimpleIDN would convert that part as well, meaning SimpleIDN does not expect the http:// 
simple.rb 
require 'simpleidn'
puts SimpleIDN.to_ascii('reseñas.li')
puts SimpleIDN.to_ascii('http://reseñas.li')

$ ruby simple.rb
xn--reseas-zwa.li
xn--http://reseas-skb.li