add example. uses edit distances and a result table

perl6 examples/edit_distances.p6
    <pre><code>
    Testing lengths:
    $str1 = 4       $str1 = 5
    O-------------------------------------------O------------O------------O------O-----O
    | func                                      | start      | end        | diff | avg |
    |----------------------------------------------------------------------------------|
    | Text::Levenshtein::Damerau::{"&dld"}      | 1415165721 | 1415165722 | 1    | 0.1 |
    | Text::Levenshtein::Damerau::{"&ld"}       | 1415165722 | 1415165722 | 0    | 0   |
    O-------------------------------------------O------------O------------O------O-----O
    Testing lengths:
    $str1 = 20      $str1 = 25
    O-------------------------------------------O------------O------------O------O-----O
    | func                                      | start      | end        | diff | avg |
    |----------------------------------------------------------------------------------|
    | Text::Levenshtein::Damerau::{"&dld"}      | 1415165722 | 1415165724 | 2    | 0.2 |
    | Text::Levenshtein::Damerau::{"&ld"}       | 1415165724 | 1415165726 | 2    | 0.2 |
    O-------------------------------------------O------------O------------O------O-----O
    Testing lengths:
    $str1 = 80      $str1 = 100
    O-------------------------------------------O------------O------------O------O-----O
    | func                                      | start      | end        | diff | avg |
    |----------------------------------------------------------------------------------|
    | Text::Levenshtein::Damerau::{"&dld"}      | 1415165727 | 1415165758 | 31   | 3.1 |
    | Text::Levenshtein::Damerau::{"&ld"}       | 1415165758 | 1415165792 | 34   | 3.4 |
    O-------------------------------------------O------------O------------O------O-----O
</code></pre>