Fix polyglot morpheme error by replacing with NLTK SnowballStemmer

[jalajthanaki]

Fix polyglot morpheme error by replacing with NLTK SnowballStemmer

Summary

This PR addresses the HTTP 403 error that occurs when running 3_1_wordsteam.py due to the polyglot library's data server (http://polyglot.cs.stonybrook.edu/~polyglot) being unavailable. The fix replaces polyglot's morphological analysis with NLTK's SnowballStemmer and updates the code to Python 3 syntax.

Changes made:

• Replaced polyglot Word objects and .morphemes with NLTK's SnowballStemmer
• Updated all print statements from Python 2 to Python 3 syntax
• Updated installation documentation to note polyglot deprecation
• Tested the script successfully runs and produces output

⚠️ Important: This changes the functionality from morphological segmentation to stemming. The output semantics are different - the original showed morpheme breakdowns, the new version shows stems only.

Review & Testing Checklist for Human

• Critical: Verify output is pedagogically acceptable - The original code showed morpheme segmentation (e.g., breaking words into meaningful units), but the replacement only shows stemming (root form). Review if this maintains the educational value for Chapter 3.
• Test the script end-to-end - Run python ch3/3_1_wordsteam.py and verify output matches book's expectations
• Check for other polyglot usage - Search the repository for other files using polyglot that may have the same issue
• Verify Python version consistency - This changes the file to Python 3. Check if other book examples are Python 2 or 3
• Review if book text needs updates - The chapter text/examples may reference morpheme output that will now look different

Test Plan

cd ch3
python 3_1_wordsteam.py
# Verify output shows appropriate stems and no errors

Notes

• The polyglot library itself still works, but its data server is permanently unavailable, making morpheme analysis impossible
• SnowballStemmer provides similar but not identical functionality - it's stemming, not morphological segmentation
• This is a functional change, not just a bug fix, so careful review is needed

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Link to Devin run: https://app.devin.ai/sessions/83802e4ce3e64ba38e388398c9c423f5
Requested by: jalajthanaki@gmail.com (@jalajthanaki)

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