New Python module release: RerankingParser updated, ModelFetcher added
python/bllipparser/RerankingParser.py: Various improvements.
    Sentence class now ensures tokens are strings to reduce crashing.
    RerankingParser class:
    -   load_unified_model_dir() renamed to
        from_unified_model_dir(), old method name is deprecated now.
    -   Parser options can now be changed with the set_parser_options()
        method.
    -   parse() and parse_tagged() both default to a new rerank
        mode, rerank='auto', which will only rerank if a reranker model
        is available.
    -   parse_tagged() now throws a ValueError if you provide an invalid
        POS tag (instead of segfaulting)
    -   check_loaded_models() renamed to _check_loaded_models() since it's
        not intended for users.
    -   added get_unified_model_parameters() helper function which
        provides paths to parser and reranker model files.
python/bllipparser/ModelFetcher.py: new Python module which downloads
    and installs BLLIP unified parsing models. Can be used via command
    line or Python library.
python/bllipparser/ParsingShell.py: can now be launched without parsing
    models
README-python.txt: docs, examples updated. Now covers ModelFetcher
    and ParsingShell (the latter was previously distributed but not
    mentioned)
setup.py: updated with latest release information