handle doubled up recurring list items

[scottleedavis]

Closes: #113

[codecov]

Codecov Report

Merging #130 into master will increase coverage by 0.13%.
The diff coverage is 50%.

@@            Coverage Diff             @@
##           master     #130      +/-   ##
==========================================
+ Coverage   52.82%   52.95%   +0.13%     
==========================================
  Files          12       12              
  Lines        3008     3008              
==========================================
+ Hits         1589     1593       +4     
+ Misses       1216     1212       -4     
  Partials      203      203

Impacted Files	Coverage Δ
server/occurrence.go	58.48% <0%> (+0.49%)	⬆️
server/list.go	51.45% <52.38%> (ø)	⬆️

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