Allow for more flexible microdata inputs

[jdebacker]

This PR adds functionality to make it straightforward for users to use the CPS, PUF, and TMD files that Tax-Calculator is compatible with. It also preserves the ability to include a custom data file, but adds arguments to pass custom grow factors and weights with the data.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 35.37415% with 95 lines in your changes missing coverage. Please review.

Project coverage is 79.50%. Comparing base (8b9fba3) to head (782931e).

Files	Patch %	Lines
taxbrain/taxbrain.py	31.70%	56 Missing ⚠️
cs-config/cs_config/helpers.py	11.11%	16 Missing ⚠️
cs-config/cs_config/functions.py	25.00%	15 Missing ⚠️
taxbrain/tests/test_brain.py	70.83%	7 Missing ⚠️
setup.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #202      +/-   ##
==========================================
- Coverage   83.13%   79.50%   -3.63%     
==========================================
  Files          23       23              
  Lines        1844     1947     +103     
==========================================
+ Hits         1533     1548      +15     
- Misses        311      399      +88     

Flag	Coverage Δ
unittests	79.50% <35.37%> (-3.63%)	⬇️

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[jdebacker]

@andersonfrailey This PR is ready for review. I'd appreciate if you could look over my changes to the API to make sure there's nothing Tax-Brain would lose from my proposed changes.