Support timezone-aware datetimes in naturaltime

[tandav]

Fixes #17

Changes proposed in this pull request:

• support timezone-aware datetimes in naturaltime

example:

>>> import datetime
>>> import humanize
>>> dt = datetime.datetime.now(tz=datetime.timezone.utc)
>>> humanize.naturaltime(dt)
'now'

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.06%. Comparing base (bdc5cb6) to head (ed6c3b0).
Report is 157 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #100   +/-   ##
=======================================
  Coverage   99.05%   99.06%           
=======================================
  Files           9        9           
  Lines         743      749    +6     
=======================================
+ Hits          736      742    +6     
  Misses          7        7           

Flag	Coverage Δ
macos-latest	97.86% <100.00%> (+0.01%)	⬆️
ubuntu-latest	97.86% <100.00%> (+0.01%)	⬆️
windows-latest	95.99% <100.00%> (+0.03%)	⬆️

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[tandav]

UPD: I don't have rights to assign a label to PR, so label check pipeline failed

[hugovk]

Thank you!