Updated I/O to use preflibtools

[Simon-Rey]

No description provided.

[codecov-commenter]

Codecov Report

Merging #73 (e2582c1) into master (99e7922) will increase coverage by 0.11%.
The diff coverage is 80.70%.

❗ Current head e2582c1 differs from pull request most recent head 9ca45bf. Consider uploading reports for the commit 9ca45bf to get more accurate results

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@@            Coverage Diff             @@
##           master      #73      +/-   ##
==========================================
+ Coverage   91.76%   91.88%   +0.11%     
==========================================
  Files          11       11              
  Lines        3400     3364      -36     
  Branches     1072     1062      -10     
==========================================
- Hits         3120     3091      -29     
+ Misses        161      156       -5     
+ Partials      119      117       -2     

Impacted Files	Coverage Δ
abcvoting/fileio.py	81.36% <80.70%> (+0.14%)	⬆️

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