Improve hiding of drop-down

[j4321]

• Improve handling of event of the calendar to hide it when the user clicks outside the window, also works for dragging the calendar
• Remove the binding to on master

[codecov[bot]]

Codecov Report

Merging #4 into master will increase coverage by 0.21%. The diff coverage is 87.5%.

@@            Coverage Diff             @@
##           master       #4      +/-   ##
==========================================
+ Coverage   93.09%   93.31%   +0.21%     
==========================================
  Files           2        2              
  Lines         739      733       -6     
==========================================
- Hits          688      684       -4     
+ Misses         51       49       -2

Impacted Files	Coverage Δ
tkcalendar.py	93.14% <87.5%> (+0.29%)	:arrow_up:

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