Update column names in retail demo

[Seth-Rothschild]

close #103

[codecov-io]

Codecov Report

Merging #104 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #104      +/-   ##
==========================================
+ Coverage   87.65%   87.66%   +0.01%     
==========================================
  Files          73       73              
  Lines        7192     7193       +1     
==========================================
+ Hits         6304     6306       +2     
+ Misses        888      887       -1

Impacted Files	Coverage Δ
featuretools/demo/retail.py	100% <100%> (ø)	⬆️
featuretools/tests/demo_tests/test_demo_data.py	100% <100%> (ø)	⬆️
featuretools/utils/gen_utils.py	64.44% <0%> (-2.23%)	⬇️
featuretools/entityset/entityset.py	90.2% <0%> (+0.44%)	⬆️

---

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 3be6fb3...7a45f7c. Read the comment docs.

[kmax12]

Looks great!