Moved color-disabling into parse_parser to fix subparsers

[RobertoRoos]

Also fixes tests. Before, nested ArgumentParsers wouldn't have their color setting changed.

Resolves #83

[codecov]

Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 46.77%. Comparing base (cf1fbb7) to head (66713cc).

Files with missing lines	Patch %	Lines
sphinxarg/parser.py	0.00%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #84      +/-   ##
==========================================
- Coverage   46.86%   46.77%   -0.10%     
==========================================
  Files          12       12              
  Lines         958      960       +2     
  Branches      205      206       +1     
==========================================
  Hits          449      449              
- Misses        468      469       +1     
- Partials       41       42       +1     

Flag	Coverage Δ
unittests	46.77% <0.00%> (-0.10%)	⬇️

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[RobertoRoos]

CI is failing because of #82 - I'd suggest we go ahead and merge this and rebase other fixes on top of it.