Remove rpy2 dependency

[jdebacker]

This PR removes the rpy2 dependency by replacing the .RData files with zipped CSV files.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.51%. Comparing base (e994433) to head (d7ee0fb).

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #115       +/-   ##
===========================================
- Coverage   73.15%   46.51%   -26.65%     
===========================================
  Files          11       17        +6     
  Lines         868     1363      +495     
===========================================
- Hits          635      634        -1     
- Misses        233      729      +496     

Flag	Coverage Δ
unittests	46.51% <100.00%> (-26.65%)	⬇️

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Files	Coverage Δ
ogusa/__init__.py	100.00% <100.00%> (ø)
ogusa/psid_data_setup.py	98.78% <100.00%> (-0.08%)	⬇️

... and 5 files with indirect coverage changes

[jdebacker]

@rickecon This PR is ready for review.

[rickecon]

@jdebacker. This PR is ready to merge. I restarted the CI and saw all the tests pass. I committed one change to the CHANGELOG.md file, which made all the tests re-run. I will merge this PR as soon as all the test run again. But I saw the Windows tests work. This PR successfully puts the Windows tests back in. Nice fix.