== Comparable#cmp

  require 'facets/comparable/cmp'

on integers

  3.cmp(4).assert == -1
  3.cmp(3).assert ==  0
  3.cmp(2).assert ==  1

on strings

  "abc".cmp("abc").assert == 0
  "abc".cmp("abcd").assert == -1
  "abcd".cmp("abc").assert ==  1
  "abc".cmp("bcd").assert == -1
  "bcd".cmp("abc").assert ==  1

