Implement tr

[peschwa]

For reference: https://rt.perl.org/Public/Bug/Display.html?id=62064

[moritz]

Sorry to not have a more useful comment, but you seem to have some debug output left in method Int.

[peschwa]

Rebased it down to one commit in a fit of wanting to make it neater. The debug output is gone, the method itself as well. It got replaced with a new class StrDistance which is described in the commit message as follows, and hopefully actually does what I described. :)

StrDistance takes the untransliterated and transliterated Strings as
constructor arguments and implements .Bool, .Int and .Numeric. Numeric
defers to .Int, which calculates the replaced characters on invocation.
Bool returns True if any transliteration has occured, False otherwise.

[peschwa]

This gist has my spectest results. There were run with current roast and the branch for this PR with newer commits merged.