removed all mentions of allow_where

[alexjwang]

Fixes #474

Removed:
allow_where variable in aggregation_primitive_base.py
allow_where variable in primitive_base.py
test_allow_where() entire function in test_deep_feature_synthesis.py

[codecov]

Codecov Report

Merging #587 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #587      +/-   ##
==========================================
- Coverage   96.44%   96.43%   -0.01%     
==========================================
  Files         117      117              
  Lines        9534     9522      -12     
==========================================
- Hits         9195     9183      -12     
  Misses        339      339

Impacted Files	Coverage Δ
...ools/primitives/base/aggregation_primitive_base.py	100% <ø> (ø)	⬆️
featuretools/synthesis/deep_feature_synthesis.py	96.74% <ø> (-0.02%)	⬇️
featuretools/primitives/base/primitive_base.py	100% <ø> (ø)	⬆️
...ols/tests/synthesis/test_deep_feature_synthesis.py	100% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 86e6d2b...eb0b35a. Read the comment docs.

[gsheni]

looks good.