Prepare PUF tests for nu06

[Peter-Metz]

The Tax-Data project recently replaced nu05 with nu06 in the PUF (see PSLmodels/taxdata#329). This PR brings Tax-Calculator tests up to speed with the change. Note a slight change of logic in test_puf_var_stats.py so that correlation coefficients are just tested for variables with "taxdata_puf" in records_variables.json.

cc @MattHJensen @andersonfrailey

Edit: Not sure why Travis is failing. Everything passes locally and the Travis log is hard to decipher

Note: the puf.csv file used for this PR was generated with the taxdata Makefile (i.e. make puf-files). As of 8/6, the updated puf.csv has not been distributed to users.

[codecov]

Codecov Report

Merging #2443 into master will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2443   +/-   ##
=======================================
  Coverage   99.92%   99.92%           
=======================================
  Files          13       13           
  Lines        2577     2582    +5     
=======================================
+ Hits         2575     2580    +5     
  Misses          2        2           

Impacted Files	Coverage Δ
taxcalc/utils.py	100.00% <0.00%> (ø)

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[MattHJensen]

Thanks @Peter-Metz, merging.