fix(Dropdown):make active dropdown item scroll into view on open

[mchirkin]

Fix #1388

[codecov-io]

Codecov Report

Merging #1465 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1465      +/-   ##
==========================================
+ Coverage   99.74%   99.74%   +<.01%     
==========================================
  Files         141      141              
  Lines        2363     2369       +6     
==========================================
+ Hits         2357     2363       +6     
  Misses          6        6

Impacted Files	Coverage Δ
src/modules/Dropdown/Dropdown.js	100% <100%> (ø)	✅
src/modules/Search/Search.js	100% <0%> (ø)	✅
src/elements/Input/Input.js	100% <0%> (ø)	✅

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[levithomason]

Looks great, thanks! I'll push a test for this and merge.

[levithomason]

Released in semantic-ui-react@0.67.2.