Provide README to Wikipedia parser example

[hunterhector]

This PR fixes #702.

Description of changes

1. Added README to instruct how to run the script
2. Provide sample data to test the script
3. Provide a download script to get the full dataset
4. Fix a few glitches in the example script

Possible influences of this PR.

Describe what are the possible side-effects of the code change.

Test Conducted

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[codecov]

Codecov Report

Merging #708 (3f1755f) into master (d9b90fb) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #708   +/-   ##
=======================================
  Coverage   80.86%   80.86%           
=======================================
  Files         243      243           
  Lines       17996    17996           
=======================================
  Hits        14552    14552           
  Misses       3444     3444           

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