Removed Sift4 text diff algorithm and replaced it with PHP's built in levenshtein algorithm. Sift4 was too greedy and would return suggestions unrelated to the user's input.
Added in memory cache of DNS domain validation results. This improves performance when validating multiple emails in a row.
Added character transposition handling to improve suggestions since levenshtein doesn't account for transpositions.
Added "off by one character" handling to improve suggestions where the user is missing the last character of the domain.
Added second level domain overrides to improve gmail suggestions.
Added command line script for validating csv files of emails.