fix(Dropdown): fix compatibility with IE

[layershifter]

Fixes #1315.

[codecov-io]

Codecov Report

Merging #1667 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1667      +/-   ##
==========================================
+ Coverage   99.75%   99.75%   +<.01%     
==========================================
  Files         141      141              
  Lines        2408     2410       +2     
==========================================
+ Hits         2402     2404       +2     
  Misses          6        6

Impacted Files	Coverage Δ
src/modules/Dropdown/Dropdown.js	100% <100%> (ø)	⬆️

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[levithomason]

@cattermo does this PR resolve your issue?

[cattermo]

It works!

Sorry for the delay, I thought I could npm install the branch from github directly but couldn't get it to work (corporate firewall...). Ended up copypasting the new code right into node_modules which proved working fine for testing purpuse.

[levithomason]

Thanks for the testing and report @cattermo.

[levithomason]

Released in semantic-ui-react@0.68.4.