Remove toolz direct dependency

[rwedge]

This pr removes the one place we directly import the toolz library. It will still get installed due to other dependencies.

[codecov]

Codecov Report

Merging #755 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #755      +/-   ##
==========================================
+ Coverage   97.68%   97.68%   +<.01%     
==========================================
  Files         118      118              
  Lines       10549    10550       +1     
==========================================
+ Hits        10305    10306       +1     
  Misses        244      244

Impacted Files	Coverage Δ
featuretools/tests/utils_tests/test_cli_utils.py	100% <100%> (ø)	⬆️
featuretools/utils/cli_utils.py	55.31% <100%> (ø)	⬆️
...aturetools/tests/entityset_tests/test_timedelta.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 81b9f20...8506ebb. Read the comment docs.

[kmax12]

LGTM