title: yii2 grid filter type not working
body: <p>I am using kartik grid lib in yii2</p>
  
  <ol>
  <li><p>This works.</p>
  
  <pre><code>[
  'attribute' =&gt; 'status',
  'filterType' =&gt; GridView::FILTER_SELECT2,
  'filter' =&gt; ['Active' =&gt; 'Active', 'In Active' =&gt; 'In Active'],
  'filterWidgetOptions' =&gt; [
      'pluginOptions' =&gt; ['allowClear' =&gt; true],
  ],
  'filterInputOptions' =&gt; ['placeholder' =&gt; 'Select'],
  ]
  </code></pre></li>
  <li><p>But this doesn't</p>
  
  <pre><code>[
  'attribute' =&gt; 'status',
  'filterType' =&gt; '\kartik\widgets\Select2',
  'filter' =&gt;['Active' =&gt; 'Active', 'In Active' =&gt; 'In Active'],
  'filterWidgetOptions' =&gt; [
      'pluginOptions' =&gt; ['allowClear' =&gt; true],
  ],
  'filterInputOptions' =&gt; ['placeholder' =&gt; 'Select'],
  ]
  </code></pre></li>
  </ol>
  
  <p>Why ? I need to use the point 2 approach. But it is not working.</p>