Implementing Country Code and Sub Region Codes as variable types

[jxwolstenholme]

No description provided.

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #430 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #430      +/-   ##
==========================================
+ Coverage   96.24%   96.25%   +<.01%     
==========================================
  Files          93       93              
  Lines        8447     8455       +8     
==========================================
+ Hits         8130     8138       +8     
  Misses        317      317

Impacted Files	Coverage Δ
featuretools/tests/testing_utils/mock_ds.py	87.76% <100%> (+0.17%)	⬆️
featuretools/variable_types/variable.py	97.29% <100%> (+0.15%)	⬆️
featuretools/entityset/entity.py	95.65% <0%> (ø)	⬆️

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[jxwolstenholme]

Will add tests and docs

[kmax12]

This is looking good. Ready to merge after my two comments are addressed. Thank you for the contribution!

[kmax12]

Looks good to me. Thank you very much for the contribution.