Add additional tests for primitives

[Seth-Rothschild]

There were 4 tests found that were not being run. Three had to do with symbol overrides and one was testing arithmetic on ordinals. Added functionality for adding and subtracting ordinals.

[codecov-io]

Codecov Report

Merging #137 into master will increase coverage by 1.4%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master     #137     +/-   ##
=========================================
+ Coverage   88.68%   90.08%   +1.4%     
=========================================
  Files          76       75      -1     
  Lines        7845     7785     -60     
=========================================
+ Hits         6957     7013     +56     
+ Misses        888      772    -116

Impacted Files	Coverage Δ
.../feature_function_tests/test_transform_features.py	98.85% <100%> (+11%)	⬆️
...utational_backend/test_calculate_feature_matrix.py	99.11% <0%> (-0.44%)	⬇️
featuretools/tests/utils_tests/test_config.py
featuretools/primitives/binary_transform.py	89.88% <0%> (+0.59%)	⬆️
featuretools/config.py	78.84% <0%> (+7.76%)	⬆️
featuretools/primitives/primitive_base.py	85.95% <0%> (+8.02%)	⬆️

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[kmax12]

Great! Merging