Implement using CharNN

[lokijuhy]

LKK confused about ElmoEmbedder() - outputs 3 vectors per input token- how use? See 05_lkk_elmo_tutorial_2_again.ipynb. I created a semantic search and tried it using each of the three output vectors, and the first one works ok but not great (the docs say the first vector is not context-based) and the other 2 vectors create nonsense results.