Clean up logging file

[bast0006]

• stick formats up top for easy editing
• strip the colored_formatter as coloredlogs INSTALL does that for us
• remove commented code
• move logger silencing below instantiation so there's no need to ever do one twice
• utilize pathlib methods for making logging dir, no need for os after it's removed

Closes #40

[codecov[bot]]

Codecov Report

Merging #41 (e97962e) into main (9b51ff5) will not change coverage. The diff coverage is 0.00%.

@@          Coverage Diff          @@
##            main     #41   +/-   ##
=====================================
  Coverage   0.00%   0.00%           
=====================================
  Files          5       5           
  Lines        294     289    -5     
=====================================
+ Misses       294     289    -5     

Impacted Files	Coverage Δ
modmail/__init__.py	0.00% <0.00%> (ø)

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