Avoid stacking "expanding" primitives

[Seth-Rothschild]

This PR prevents DFS from trying to stack on primitives which output "expanding" features. It is resolves the error from #85.

[codecov-io]

Codecov Report

Merging #238 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #238      +/-   ##
==========================================
+ Coverage   93.64%   93.65%   +0.01%     
==========================================
  Files          71       71              
  Lines        7690     7697       +7     
==========================================
+ Hits         7201     7209       +8     
+ Misses        489      488       -1

Impacted Files	Coverage Δ
featuretools/synthesis/deep_feature_synthesis.py	93.27% <100%> (+0.05%)	⬆️
...ols/tests/feature_function_tests/test_agg_feats.py	98.55% <100%> (+0.02%)	⬆️
featuretools/utils/gen_utils.py	66.66% <0%> (+2.22%)	⬆️

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[kmax12]

we can move this check inside of the loop a couple lines down where we also loop over each input.

also, let's add a test case for this.

[Seth-Rothschild]

Working on the test case.

For moving this inside the for loop, want me to also move the check for base_of_exclude which can also be placed inside the larger loop?

[kmax12]

Looks good. Merging