[WIP] fix pooch data cacheing

[atravitz]

downstream of #58

looks like the original cacheing strategy was breaking, so I dropped it in #58, and I'm addressing it separately here.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.16%. Comparing base (5260e3b) to head (a1ee886).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #61   +/-   ##
=======================================
  Coverage   88.16%   88.16%           
=======================================
  Files           7        7           
  Lines         338      338           
=======================================
  Hits          298      298           
  Misses         40       40           

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