Returns the levenshtein distance between s1 and s2 - a cost of
1 per character insertion, deletion or update. Runs in
quadratic time and linear memory.

`(edit-distance "same" "same")`

`=> 0`

`(edit-distance "same" "sand")`

`=> 2`

`(edit-distance "Saturday" "Sunday")`

`=> 3`

`(find-nearest-edits str str-ls [max-distance])`

Returns a list of strings in `str-ls`

with the smallest
edit distance to `str`

, preserving order. If
`max-distance`

is provided and positive, only return if
the edits are less or equal to that distance.