28-million bug fix

[jakewilliami]

julia> spelled_out(104464112)
"one hundred four million, four hundred sixty-four thousand, one hundred twelve"

julia> spelled_out(371318354)
"three hundred seventy-one million, three hundred eighteen thousand, three hundred fifty-four"

julia> spelled_out(28589987) # INCORRECT
"thirty-eight million, five hundred eighty-nine thousand, nine hundred eighty-seven"

julia> spelled_out(46688538)
"forty-six million, six hundred eighty-eight thousand, five hundred thirty-eight"