decorator @py3_data for use with the file pointers in data.py
* for use on the initializers, e.g. BufferedGzipFile
* adds PY3/ to the data path for the following datasets:

  chunkers/maxent_ne_chunker
  help/tagsets
  taggers/maxent_treebank_pos_tagger
  tokenizers/punkt
apply @py3_data decorator to the path pointer init methods, to add PY3 to paths for selected corpora
Merge pull request #474 from wooters/master

Fixed doctests involving dict objects
merge framenet corpus reader from nschneid:patch-5, resolves https://github.com/nltk/nltk/pull/473
Merge pull request #470 from stevenbird/master

decorator @py3_data for use with the file pointers in data.py
Add missing import for py3_data decorator
testing fix: nltk.clean_html was deprecated/removed
nltk.sem.chat80: raise ImportError exception when sqlite3 is not available.

This code previously raised NameError in such cases.
testing fix: don't import from deprecated and removed sklearn.svm.sparse
framenet.py: link together objects rather than storing pointers
framenet.py: Python 3 compatibility
Merge pull request #482 from nschneid/patch-6

framenet.py: link together objects rather than storing pointers; new propagate_semtypes() method