Tests for CheckboxStyle & RadioStyle

[AydinHassan]

I also refactored hasChangedFromDefaults. I prefer this way where we don't need an extra property and to litter each setter with a flag set.

[codecov-io]

Codecov Report

Merging #213 into master will increase coverage by 0.47%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #213      +/-   ##
============================================
+ Coverage     93.04%   93.52%   +0.47%     
  Complexity      558      558              
============================================
  Files            30       30              
  Lines          1667     1667              
============================================
+ Hits           1551     1559       +8     
+ Misses          116      108       -8

Impacted Files	Coverage Δ	Complexity Δ
src/Style/RadioStyle.php	100% <100%> (+11.76%)	12 <0> (ø)	⬇️
src/Style/CheckboxStyle.php	100% <100%> (+11.76%)	12 <0> (ø)	⬇️

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