Use the Python bindings for CRF++

[desilinguist]

Right now, we are using the crf_learn and crf_test command line programs directly. We should look into using the Python bindings for CRF++ that are included in the package.

[aoifecahill]

OR alternatively, we could consider something like https://sklearn-crfsuite.readthedocs.io/en/latest/

[srhrshr]

@aoifecahill @desilinguist, I have used both crf++ and sklearn-crfsuite in the past. So, let me know if this is something you want me to look into?

If so, I'd need few inputs from you during the porting from crf++ to crfsuite particularly regarding the feature template and the c values. Thanks!

[desilinguist]

@srhrshr if you have the time to look into this, it'd be great!