Fix #19, add test case

[nicolaiunrein]

This PR fixes #19.
I Modified the clone method so that it also copies the fields _captureNames and _implodeString. If it does not make sense to add the _implodeString field feel free to remove it. I just looked at the code briefly in order to resolve #19 as I ran into the same problem myself and needed it to be fixed.

[codecov-commenter]

Codecov Report

Merging #20 (c5f640c) into master (79a8fd1) will increase coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head c5f640c differs from pull request most recent head a313f8e. Consider uploading reports for the commit a313f8e to get more accurate results

@@            Coverage Diff             @@
##           master      #20      +/-   ##
==========================================
+ Coverage   96.83%   96.84%   +0.01%     
==========================================
  Files          19       19              
  Lines         505      507       +2     
  Branches       73       73              
==========================================
+ Hits          489      491       +2     
  Misses         16       16              

Impacted Files	Coverage Δ
lib/Builder.js	97.08% <100.00%> (+0.02%)	⬆️

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