init dev and update contributors
removed reference to waffle.io from contributing guidelines
removed dependency on nltk's depricated 'PunktWordTokenizer' and replaced it with 'TreebankWordTokenizer' see https://github.com/nltk/nltk/pull/746#issuecomment-57625756 for details
updated docs
updated docs
udpated README.md
Release 0.4.1
Merge branch 'release/0.4.1'