fix(Dropdown): fix call order of onAddItem and onChange handlers

[layershifter]

Fixes #2106.

[codecov-io]

Codecov Report

Merging #2113 into master will increase coverage by 14.79%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           master    #2113       +/-   ##
===========================================
+ Coverage   84.97%   99.76%   +14.79%     
===========================================
  Files         150      150               
  Lines        2596     2596               
===========================================
+ Hits         2206     2590      +384     
+ Misses        390        6      -384

Impacted Files	Coverage Δ
src/modules/Dropdown/Dropdown.js	100% <100%> (ø)	⬆️
src/modules/Modal/Modal.js	100% <0%> (+3.94%)	⬆️
src/modules/Progress/Progress.js	100% <0%> (+4.76%)	⬆️
src/modules/Tab/Tab.js	100% <0%> (+10.52%)	⬆️
src/views/Card/Card.js	100% <0%> (+20%)	⬆️
src/modules/Sticky/Sticky.js	100% <0%> (+31.64%)	⬆️
src/modules/Transition/Transition.js	100% <0%> (+53.42%)	⬆️
src/modules/Modal/ModalHeader.js	100% <0%> (+62.5%)	⬆️
src/modules/Popup/PopupHeader.js	100% <0%> (+62.5%)	⬆️
src/modules/Popup/PopupContent.js	100% <0%> (+62.5%)	⬆️
... and 8 more

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[levithomason]

Released in semantic-ui-react@0.74.0