title: Semantic-UI-React, selection, multi, can't set defaultValue
body: <p>I have React component:</p>
  
  <pre><code>&lt;Dropdown
      placeholder={field[propName].label}
      id={propName}
      fluid
      multiple
      selection
      search
      defaultValue={defaultOptions}
      options={options}
  /&gt;
  </code></pre>
  
  <p>So <code>options</code> and <code>defaultOptions</code> is the same structure arrays <code>{text: 'string, value: 'string'}</code>.</p>
  
  <p>In semantic UI source code I found this:</p>
  
  <pre><code>/** Initial value or value array if multiple. */
      defaultValue: PropTypes.oneOfType([
        PropTypes.string,
        PropTypes.number,
        PropTypes.arrayOf(PropTypes.oneOfType([
          PropTypes.string,
          PropTypes.number,
        ])),
      ])
  </code></pre>
  
  <p>That the reason why my code above gives me error: </p>
  
  <pre><code>`Warning: Failed propType: Invalid prop `defaultValue` supplied to `Dropdown`. Check the render method of `View`.`
  </code></pre>
  
  <p>So question is how then I should set defaultValue for multi selection type of Dropdown?</p>