use .getNode and .getNodes if available for implicit updates

[jwbay]

Fixes #27

[codecov-io]

Codecov Report

Merging #62 into master will increase coverage by 0.2%.
The diff coverage is 100%.

@@           Coverage Diff            @@
##           master     #62     +/-   ##
========================================
+ Coverage      96%   96.2%   +0.2%     
========================================
  Files           5       5             
  Lines          75      79      +4     
  Branches       32      34      +2     
========================================
+ Hits           72      76      +4     
  Misses          2       2             
  Partials        1       1

Impacted Files	Coverage Δ
src/shallow.js	100% <100%> (ø)	⬆️

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[adriantoine]

Thanks for your contribution! 🎉