Some simple improvements

[rdbende]

[codecov[bot]]

Codecov Report

Merging #80 (3f8ac80) into master (1a8ce0c) will decrease coverage by 0.26%. The diff coverage is 79.22%.

@@            Coverage Diff             @@
##           master      #80      +/-   ##
==========================================
- Coverage   89.51%   89.24%   -0.27%     
==========================================
  Files          43       43              
  Lines        4026     4065      +39     
==========================================
+ Hits         3604     3628      +24     
- Misses        422      437      +15     

Impacted Files	Coverage Δ
ttkwidgets/frames/toggledframe.py	75.92% <72.91%> (-24.08%)	:arrow_down:
ttkwidgets/linklabel.py	93.54% <89.28%> (-2.89%)	:arrow_down:
ttkwidgets/itemscanvas.py	95.77% <100.00%> (ø)
ttkwidgets/checkboxtreeview.py	93.18% <0.00%> (+0.32%)	:arrow_up:

---

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 1a8ce0c...3f8ac80. Read the comment docs.

[rdbende]

And while we are here, shouldn't we replace the uses of kwargs.pop with individual keyword arguments, and default values? After all, ttkwidgets needs Python 3, so it's not a big deal. (In a separate PR of course).