Created by: ysds
This PR fix the difference between the dropup demo and the example code.
http://getbootstrap.com/docs/4.0/components/dropdowns/#dropup-variation
Demo:
<button type="button" class="btn btn-secondary dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropup
</button>
Example code:
<button type="button" class="btn btn-secondary">Dropup</button>
<button type="button" class="btn btn-secondary dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
<span class="sr-only">Toggle Dropdown</span>
</button>