* Port NLTKDocumentSplitter from dC to Haystack
* Improve pydocs
* Use haystack logging
* Add NLTKDocumentSplitter to __init__.py
* Use haystack logging, rename test classes
* Fixing _needs_join return
* Linting
* PR feedback
* More static methods
* Increase test coverage
* Compile pattern
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Co-authored-by: Sebastian Husch Lee <sjrl@users.noreply.github.com>
