`toJSON` should persist minimal data

Hi, This is in fact a very nice implementation thanks a lot !!!

However these is one major problem, if someone wants to store a giant list of words in the Trie, then reusing it is the real deal I guess (transferred over the wire for example).
thus, toJSON must to my opinion really output as minimal data as possible. the bet if possible is to have a model lighter than the array of strings in ascci.

I don't know what's meta associated with each token, if not necessary, omit that for instance.

Thanks anyway :)