setup for next development stage
added NP Extractor with tests
add NP Extractor to feature list
NP extractor has to be instance of BaseNPExtractor, plus added link to pip issue on Windows to README
bumped dev version
refactored tool specific arguments and keyword arguments are passed on to the individual tools and tweaked NP Extractor
added blob.noun_phrases example to README
updated version and history for release 0.2.1
Merge remote-tracking branch 'origin/dev' for release 0.2.1
updated README for master branch