Fix #88 and add zipfile test

[jrideout]

backs out the pathlib change in #88 (which didn't quite work and requires py3.9) and added a test file for the duplicate filename in a zip case

[codecov]

Codecov Report

Merging #103 (8a4a519) into master (e874f08) will increase coverage by 0.22%.
The diff coverage is 94.11%.

@@            Coverage Diff             @@
##           master     #103      +/-   ##
==========================================
+ Coverage   95.97%   96.20%   +0.22%     
==========================================
  Files           7        7              
  Lines        1292     1290       -2     
  Branches      120      120              
==========================================
+ Hits         1240     1241       +1     
+ Misses         36       34       -2     
+ Partials       16       15       -1     

Impacted Files	Coverage Δ
tnefparse/util.py	90.47% <0.00%> (ø)
tnefparse/mapi.py	81.32% <100.00%> (+0.11%)	⬆️
tnefparse/tnef.py	95.25% <100.00%> (+0.95%)	⬆️

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