Update to January 2020 CBO economic projections

[Peter-Metz]

This PR incorporates new input data files produced by taxdata/#331. The new data prompts updates to inflation-indexed parameters for future years and extrapolated attributes of the filing units in the (unchanged) puf.csv and cps.csv.gz files.

This comment details aggregate changes as a result of the new data.

Finally, the last simulation year is bumped from 2029 to 2030.

cc @MattHJensen

[codecov]

Codecov Report

Merging #2403 into master will not change coverage by %.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master     #2403   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           13        13           
  Lines         2751      2751           
=========================================
  Hits          2751      2751           

Impacted Files	Coverage Δ
taxcalc/growdiff.py	100.00% <100.00%> (ø)
taxcalc/policy.py	100.00% <100.00%> (ø)

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[MattHJensen]

@Peter-Metz, thanks very much for this PR and the preceding PR in TaxData. Thanks for talking with me offline about how lower inflation forecasts from CBO influence the tax law parameters. Everything here looks good to me, and I'm merging now.