Fix display issues in Windows and make config() method accept a dictionary of options

[j4321]

• Fix calendar drop-down not in front issue if window has the -topmost attribute in Windows (#49)
• Fix calendar not hiding when clicking again on DateEntry drop-down button (#51) in Windows
• Make Calendar.config() and DateEntry.config() accept a dictionary like standard tkinter widgets

[codecov[bot]]

Codecov Report

Merging #52 into master will decrease coverage by 0.09%. The diff coverage is 93.33%.

@@            Coverage Diff            @@
##           master      #52     +/-   ##
=========================================
- Coverage   93.39%   93.29%   -0.1%     
=========================================
  Files           9        9             
  Lines        1967     1983     +16     
=========================================
+ Hits         1837     1850     +13     
- Misses        130      133      +3

Impacted Files	Coverage Δ
tests/test_calendar.py	92.06% <100%> (+0.08%)	:arrow_up:
tests/test_dateentry.py	100% <100%> (ø)	:arrow_up:
tkcalendar/calendar_.py	94.79% <83.33%> (-0.09%)	:arrow_down:
tkcalendar/dateentry.py	94.78% <91.66%> (-0.95%)	:arrow_down:

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update ce9f12c...b263717. Read the comment docs.