Minor optimization for radix sort

In the radix sort code remainingPart is calculated like so:

let remainingPart = number / digits

So if the number is 1772 and the digits are 1000, then the remaining part will be 1. However, when you check whether to go for another round, you check like this:

if remainingPart > 0 {
  done = false

Since remainingPart is 1, this causes the while loop to do another unnecessary round for the 10000 digits.