This is far from complete but it should be enough to check some things.
1. Mecab transition. Janome doesn't support Unidic, only IPAdic, but UD
tag mappings are based on Unidic. This switches out Mecab for Janome to
get around that.
2. Raw tag extension. A simple tag map can't meet the specifications for
UD tag mappings, so this adds an extra field to ambiguous cases. For
this demo it just deals with the simplest case, which only needs to look
at the literal token. (In reality it may be necessary to look at the
whole sentence, but that's another issue.)
3. General code structure. Seems nobody else has implemented a custom
Tagger yet, so still not sure this is the correct way to pass the
vocabulary around, for example.
Any feedback would be greatly appreciated. -POLM
