Fix array duplication after parse

[Zwooosh]

This fixes #156 and #168.

I'm just using the suggested fix for deepMerge.

[codecov]

Codecov Report

Base: 90.92% // Head: 90.94% // Increases project coverage by +0.01% 🎉

Coverage data is based on head (6233d32) compared to base (4687b6a).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #238      +/-   ##
==========================================
+ Coverage   90.92%   90.94%   +0.01%     
==========================================
  Files           6        6              
  Lines         562      563       +1     
==========================================
+ Hits          511      512       +1     
  Misses         51       51              

Impacted Files	Coverage Δ
src/parser.js	90.21% <100.00%> (+0.02%)	⬆️

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