refactor: use object.assign and drop lodash.flatten

[JustinBeckwith]

No description provided.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@f28a750). Click here to learn what that means.
The diff coverage is 100%.

@@           Coverage Diff           @@
##             master   #362   +/-   ##
=======================================
  Coverage          ?   100%           
=======================================
  Files             ?     10           
  Lines             ?   1282           
  Branches          ?      0           
=======================================
  Hits              ?   1282           
  Misses            ?      0           
  Partials          ?      0

Impacted Files	Coverage Δ
src/instance.js	100% <100%> (ø)
src/table.js	100% <100%> (ø)
src/row.js	100% <100%> (ø)
src/filter.js	100% <100%> (ø)
src/index.js	100% <100%> (ø)

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