Fix unstable formatting of tables at column width boundary

[JohnnyMorganz]

Fixes #436

[codecov]

Codecov Report

Merging #437 (d33cb82) into master (09be20b) will increase coverage by 0.02%.
The diff coverage is 97.91%.

@@            Coverage Diff             @@
##           master     #437      +/-   ##
==========================================
+ Coverage   96.38%   96.40%   +0.02%     
==========================================
  Files          14       14              
  Lines        5194     5227      +33     
==========================================
+ Hits         5006     5039      +33     
  Misses        188      188              

Impacted Files	Coverage Δ
src/formatters/trivia_util.rs	94.32% <85.71%> (-0.12%)	⬇️
src/formatters/table.rs	98.95% <100.00%> (+0.07%)	⬆️
src/formatters/general.rs	96.87% <0.00%> (+0.20%)	⬆️

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