Re-implementating of FreqDist using Counter, cf https://github.com/nltk/nltk/issues/86
added missing import statement
py3 fixes
Merge branch 'master' of https://github.com/nltk/nltk
Merge branch 'master' of https://github.com/jskda/nltk
kludge to handle unknown tags
removed redundant copyright file
make word_tokenize behave across sentence boundaries, by incorporating Punkt
fixed index in FreqDist.max
Merge branch 'master' of https://github.com/nltk/nltk