fixed doctype regex to handle doctype tag w/o square brackets
almost fixed it; want to make the decisiontrees demo work right with the binary attribute set to true
Fix the decision stumps so that they work on Python 3, and are robust to not seeing a positive or negative examples.
Merge pull request #336 from cadaeib/fix_xmlcorpusreader

fixed doctype regex to handle doctype tag w/o square brackets
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'DavidDoukhan/master'
Merge pull request #346 from alexrudnick/master

Fix for decision trees with binary=True
applied patch from Tomonori Nagano to fix pos tag issue, resolves issue 347
fix indentation error; still an issue with line 323
re-apply patch from Nagano
Escape reserved chars in Tree.pprint_latex_qtree()
Merge pull request #348 from stesh/master

Escape reserved LaTeX characters in nltk.tree.Tree.pprint_latex_qtree()
Python 3.3 compatibility for nltk.internals.ElementWrapper. Thanks @achimnol. Fixes #350.
spelling is fixed
fixes for tkinter in nltk.app and nltk.draw packages
Merge pull request #351 from hleeldc/tkinter_fix

fixes for tkinter in nltk.app and nltk.draw packages
Merge branch 'master' of https://github.com/nltk/nltk
incorporated David Doukhan's pull request https://github.com/nltk/nltk/pull/345 , specified float return type, added doctests, misc formatting fixes
updated tests for the length-normalized unweighted version of windowdiff
Correction of the Pk metric

The first implementation I did was 100% wrong.
According to [1] Pk should provide a penalty of about 0.5 to all degenerated segmentations (empty, full, randomized), which is not statisfied by my last implementation.
It was corrected using the explantations provided in [2]

Sorry about that

[1] Beeferman D., Berger A., Lafferty J. (1999)
Statistical Models for Text Segmentation
Machine Learning, 34, 177-210

[2] Unbiased discourse segmentation evaluation
John Niekrasz and Johanna D. Moore
Spoken Language Technology Workshop (SLT), 2010 IEEE
Page(s): 43 - 48