## 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"

