Sort characters of a string (eg asdf => adfs). Exposes 3 methods, all taking an &str to return a String
vecsort: Converts arg into Vec, sorts Vec, converts Vec to String
insertsort: Builds a string by employing linear insert sort on each character
bucketsort: Builds a string by counting the occurences for all ascii characters,
building up a sorted string of non ascii characters with insert sort,
then generates a string based off counts of ascii characters & appends non ascii
insertsort is good for very small strings, bucketsort is good if you expect mostly ascii, vecsort is the only one that isn't worst case quadratic
NB bucketsort is O(N) for ascii strings