chore(coverage): remove docs from coverage reports

[layershifter]

It looks very strange to me that we include our docs to coverage reports. This PR fixes it.

[codecov-io]

Codecov Report

Merging #1283 into master will increase coverage by 3.82%.

@@            Coverage Diff             @@
##           master    #1283      +/-   ##
==========================================
+ Coverage   95.91%   99.74%   +3.82%     
==========================================
  Files         883      140     -743     
  Lines        4926     2392    -2534     
==========================================
- Hits         4725     2386    -2339     
+ Misses        201        6     -195

Impacted Files	Coverage Δ
...Examples/collections/Grid/Types/GridExampleGrid.js
...mples/elements/Step/States/StepExampleCompleted.js
...dules/Popup/Variations/PopupExampleHideOnScroll.js
...ments/Divider/Variations/DividerExampleClearing.js
docs/app/Examples/modules/Dropdown/common.js
...modules/Dropdown/States/DropdownExampleDisabled.js
...esponsiveVariations/GridExampleReversedComputer.js
...collections/Message/Types/MessageExampleMessage.js
...ions/Menu/Variations/MenuExampleColoredInverted.js
...ns/Grid/Variations/GridExampleVerticalAlignment.js
... and 733 more

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[levithomason]

Released in semantic-ui-react@0.64.8.