Adding logic for the default value when the parent is missing

[scorpioluck20]

Pull Request Description

Adding logic for the default value in _calculate_direct_features. Now, if the parent missing, the calculated value will be the default value (not a 'nan').

Fixes #682

[CLAassistant]

All committers have signed the CLA.

[scorpioluck20]

As for this Pull Request. I run 'make test' and 'make lint'. It shows error as below.

flake8 featuretools && isort --check-only --recursive featuretools
ERROR: /work/featuretools/featuretools/init.py Imports are incorrectly sorted.

After using 'make lint-fix', the error is fixed, but the code cannot be run as some modules cannot be imported. I need to check out the code to be the original one.

[codecov]

Codecov Report

Merging #688 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #688      +/-   ##
==========================================
- Coverage   97.49%   97.49%   -0.01%     
==========================================
  Files         118      118              
  Lines        9713     9731      +18     
==========================================
+ Hits         9470     9487      +17     
- Misses        243      244       +1

Impacted Files	Coverage Δ
...utational_backend/test_calculate_feature_matrix.py	99.37% <100%> (+0.01%)	⬆️
...s/computational_backends/feature_set_calculator.py	98.44% <100%> (+0.02%)	⬆️
...computational_backends/calculate_feature_matrix.py	97.89% <0%> (-0.43%)	⬇️

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[rwedge]

stale pr, closing for now. could move forward if it was updated to match current code