- Renamed "CorpusI" etc to "CorpusReaderI" etc, to make it clear that   we're providing corpus readers, not the actual copora - Updated docstrings, to make this corpus/corpus reader distinction clear. - Added CorpusReaderI.path() method - Fixed typo in CorpusReaderI.open() docstring - Removed subcorpora(), subcorpus() from CorpusReaderI, replaced them   with groups() - For __repr__, only catch IOError - Changed default behavior of CorpusReaderI.license() and   CorpusReaderI.copyright() to return 'Unknown' instead of None. - Removed license and copyright options from SimpleCorpusReader (but   retained copyright_file and license_file)
- Renamed "CorpusI" etc to "CorpusReaderI" etc, to make it clear that
  we're providing corpus readers, not the actual copora
- Updated docstrings, to make this corpus/corpus reader distinction clear.
- Added CorpusReaderI.path() method
- Fixed typo in CorpusReaderI.open() docstring
- Removed subcorpora(), subcorpus() from CorpusReaderI, replaced them
  with groups()
- For __repr__, only catch IOError
- Changed default behavior of CorpusReaderI.license() and
  CorpusReaderI.copyright() to return 'Unknown' instead of None.
- Removed license and copyright options from SimpleCorpusReader (but
  retained copyright_file and license_file)

- Added a new corpus reader for the treebank
  - 4 groups: raw, tagged, parsed, merged
  - If the merged group isn't available, then compute it on-the-fly
  - Expose the merge() method, in case anyone wants to use it.


svn/trunk@1128

nltk/nltk,nltk/nltk,nltk/nltk