Fix 153 processing with multiple $e

[nichtich]

In MARC field 153 with multiple $e all its values were concatenated instead of taking the last one only, so the URI for skos:broader was wrong. Test case rvk.xml contains an example starting at line 60.

[codecov-io]

Codecov Report

Merging #40 into master will increase coverage by 0.23%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #40      +/-   ##
==========================================
+ Coverage   78.39%   78.63%   +0.23%     
==========================================
  Files           5        5              
  Lines         699      702       +3     
==========================================
+ Hits          548      552       +4     
+ Misses        151      150       -1

Impacted Files	Coverage Δ
mc2skos/record.py	88.37% <100%> (+0.08%)	:arrow_up:
mc2skos/mc2skos.py	54.32% <0%> (+0.48%)	:arrow_up:

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[danmichaelo]

Thanks! I really wish LC had better documentation and examples on repeated subfields, it's quite hard to anticipate how repeated subfields are applied in practice just from reading the MARC21 Classification documentation.

[danmichaelo]

Merged in af68655eaacd9bcaa1c7ea64559e8e5a8fe74f81