Move logic to convert aware datetime to naive into function

[ErikKalkoken]

Fixes #122

Changes proposed in this pull request:

• Add tests for naturaltime() with when parameter and timezone aware datetimes
• Refactor logic for converting timezone aware datetimes into naive datetimes into a function

[codecov]

Codecov Report

Merging #123 (5262409) into main (fb3322a) will increase coverage by 0.00%.
Report is 12 commits behind head on main.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #123   +/-   ##
=======================================
  Coverage   99.18%   99.19%           
=======================================
  Files           9        9           
  Lines         737      746    +9     
=======================================
+ Hits          731      740    +9     
  Misses          6        6           

Flag	Coverage Δ
macos-latest	97.58% <100.00%> (+0.02%)	⬆️
ubuntu-latest	97.58% <100.00%> (+0.02%)	⬆️
windows-latest	96.11% <100.00%> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
src/humanize/time.py	100.00% <100.00%> (ø)
tests/test_time.py	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

[hugovk]

Thanks for the PR, a couple of minor suggestions.

[thedoctorjtd]

Revisions make sense; original changes should fix the issue.