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