added phrase extraction algorithm
fixed he max length for fs variable on line 34
fixed if-else condition in extract()
fixed typo error in function description.
added the doctext.
revert changes to gdfa to pre-nltk merge-pull
Merge pull request #4 from nltk/develop

Syncing fork with nltk-dev
added proper algorithm descriptions, added examples to doctests and
added target phrase position to track reordering
added the :params and :return in the docstr.
corrected mistake in the :param for the alignment input.
corrected typos in docstr and remove non :param style input/output
description.
removed comments that are transparent in the code.
untangled spaghetti code with nested functions, also used `print()` for
python3.
Merge pull request #724 from alvations/develop

Added Phrase Extraction Algorithm for Phrase-based MT in nltk.align