Make TextTransformer translateable

This fixes #43 and allows providing a translator to the TextTransformer.

By default it works fully BC and will continue to output english texts. But if you provide a configured translator with the right locale you can get texts in french or german (so far the only two I did as proof of concept that this works with more than english).

Combined with a `setlocale(LC_ALL, 'de');` for example it will also output the month/day names in the right language. I am not sure if we really want to do that or include month and day in the translation so that it is fully self-contained? setlocale can be a bit of a pain to work with depending on the system and not all locales are supported on all machines AFAIK. I am happy to do that additional change if deemed necessary.