Train and predict sentence vectors from BioScope

First draft of utilizing doc2vec for getting fixed-length feature vectors from
sentences of arbitrary length. Next step is to train a classifier with the
learnt sentence vectors and compare the model against baseline models like
Naive Bayes.
Extract and print labeled phrases from BioScope
Comment on how to redirect labeled phrases to file

I encountered a UnicodeEncodeError when piping the stdout of
extract_labeled_phrases.py to a file. I wrote a comment on how to solve this
problem.