Edit distance

[poperigby]

Supersedes #15

Help would be much appreciated for the TODO items.

TODO:

• [ ] The test_single_character_deletion doesn't seem to work for some reason.
• [x] Replace use of str.chars().nth() because it makes the function O(n^2)

[poperigby]

I fixed the second problem but this will no longer work with non-ASCII characters. Not an issue in my opinion.

[learner-long-life]

@AbyssalRemark can you check out this branch, try this code, and review it?

[learner-long-life]

For debugging edit distance https://phiresky.github.io/levenshtein-demo/

[learner-long-life]

From our debugging today, it looks like there are two problems:

• Repeated letters, as in the letter t at the end of kit vs. kitt, is currently being counted as 0 edit distance incorrectly (it should be 1)
• Matching a letter, like n at the end of kittn and kitten after a deletion (or perhaps any mismatch).