changed ContextFreeGrammar to CFG, WeightedGrammar to PCFG, and StatisticalGrammar to ProbabilisticGrammar
drop the string initialization of Tree
drop the string initialization of Tree
drop the string initialization of Tree
drop the string initialization of Tree
removed the polymorphism from the multilingual wordnet methods which would return an object or a collection of objects, depending on whether they are called with a single language or multiple languages, cf https://github.com/nltk/nltk/issues/505
updates for first beta release
fixed & updated collocations unit tests
use the original likelihood values from Dunning, CL, 1993, not sure why the values are x2 the original, they weren't present in the paper
fixed wordnet doctests now that using a list of languages are deprecated
Merge pull request #678 from jskda/pull_request.tests

Fixes to collocation unit tests
Merge pull request #676 from stevenbird/issue/657

Names for grammar classes
read `lemma`, `ctag` and `feats` columns from conll file
Merge pull request #677 from jw2013/develop

Drop the string initialization of Tree
Merge pull request #679 from nournia/conll-format

CONLL format missed columns
updated ChangeLog with info re new changes
Merge branch 'develop' into issue/656