Fixing a Bleu score bug.

If any one of the p_ns is zero, that should make the entire score zero.

An attempt to resolve #789
Don't raise an exception if sys.stdout is replaced with a stub. See GH-788.
Merge branch 'develop' of github.com:nltk/nltk into bleu_fix
bleu refactoring: removing the BLEU class.
Typo
Don’t lowercase the candidate and reference sentences.
Merge pull request #791 from dimazest/bleu_fix

Bleu score refactoring.
fixes to avoid function shadowing module name, cf #789
Added ASCII visualization of trees, modified from the disco-dop project by Andreas van Cranenburgh
support ADJ_SAT, as requested in http://stackoverflow.com/questions/26900954/why-cant-i-pass-wn-adj-sat-as-a-pos-when-requesting-synsets
correct documentation for dispersion plot
Fix _decode_stdoutdata utility for Python 3.2. See GH-788.
WordNet: lemma name lookup bugfix (#454) was clobbered
Merge pull request #799 from nschneid/patch-12

WordNet: lemma name lookup bugfix (#454) was clobbered
Renamed `Tree` method `visualize` to `pretty_print`
Renamed the class `TreeVisualizer` to `TreePrettyPrinter`.
Renamed the file `treevisualizer.py` to `treeprettyprinter`.
Merge pull request #794 from heatherleaf/treedraw

ASCII visualization of trees
Fix bug :  Stanford tokenizer -- request to add -outputFormat inlineXML #735