Distance returns the edit distance between a and b using the
Wagner-Fischer algorithm.
A and B must be less than 255 characters long.
maxDist is the maximum distance to consider.
A value of -1 for maxDist means no maximum.
Matches returns the closest matches to the needle from the haystack.
The maxDistance parameter is the maximum Matches distance to consider.
If no matches are found, an empty slice is returned.