added more functions (chunking) and others related to NP heads
More chunking features
CAUTION:
1) tree_converter can no longer import entity_types -- not sure how to fix the circular dependencies. Because of this I was not able to add the 'Washington, D.C.' sentence to the augmented tree dict.
2) evaluator_finegrained has not been tested at all
Merge branch 'julia' of https://github.com/pkarmstr/relation-extraction
merged everything, need to fix imports