Fuzzy assign bio tags

allow assign the BIO tags with fuzzy match.  this can be useful when having some of partially labelled dataset.
 
I think it may be good for `fuzzy_assign_bio_tags` to have a wrapper compatible with model (i.e. it should be a class with a 'predict' method and function parameters (pattern, etc) passed to constructor). This way one will be able to use it with NER.