== String#nchar

  require 'facets/string/nchar'

  "abcxyz".nchar(3).assert == "abc"
  "abcxyz".nchar(-3).assert == "xyz"
  "abcxyz".nchar(3, 'HI').assert == "HIxyz"
  "abcxyz".nchar(-3, 'HI').assert == "abcHI"

