Add new configuration object

[CharlesBradshaw]

Adds data_path as a static variable and a class method set_data_path to update data_path

[codecov]

Codecov Report

Merging #401 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #401      +/-   ##
==========================================
+ Coverage   95.97%   95.99%   +0.02%     
==========================================
  Files          91       92       +1     
  Lines        7945     7996      +51     
==========================================
+ Hits         7625     7676      +51     
  Misses        320      320

Impacted Files	Coverage Δ
featuretools/tests/config_tests/test_config.py	100% <100%> (ø)
featuretools/primitives/base/primitive_base.py	100% <100%> (ø)	⬆️
...retools/tests/primitive_tests/test_feature_base.py	100% <100%> (ø)	⬆️
featuretools/config_init.py	97.82% <100%> (ø)
featuretools/tests/utils_tests/test_config.py	91.42% <100%> (ø)	⬆️

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[kmax12]

Looks good to me. Ready to merge