Cumulative primitives

[CharlesBradshaw]

Fixes #405

Updated cumulative primitives (Count,Sum,Max,Min,Mean) to use new primitive API

[codecov]

Codecov Report

Merging #410 into master will increase coverage by 0.09%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #410      +/-   ##
==========================================
+ Coverage   96.14%   96.24%   +0.09%     
==========================================
  Files          92       93       +1     
  Lines        8232     8434     +202     
==========================================
+ Hits         7915     8117     +202     
  Misses        317      317

Impacted Files	Coverage Δ
featuretools/entityset/entity.py	95.65% <ø> (ø)	⬆️
featuretools/entityset/entityset.py	93.84% <ø> (ø)	⬆️
...tools/primitives/standard/cum_transform_feature.py	100% <100%> (ø)
...s/tests/primitive_tests/test_transform_features.py	98.51% <100%> (+0.46%)	⬆️

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[kmax12]

Looks good to me