title: add kartik into yii 2
body: <p>i'm a new yii 2 developer .
  i want to add kartik libary into my site and use the gridview !
  i install the kartik and when i write use kar it autocomplete  kar to kartik and this show that the libary installed .
  but when i use an empty gridview like this : </p>
  
  <pre><code>use kartik\grid\GridView;
  /*
  
  CODE
  
  */
          &lt;?= GridView::widget([
      'dataProvider' =&gt; $dataProvider,
      'filterModel' =&gt; $searchModel,
      'columns' =&gt; [
          ['class' =&gt; 'yii\grid\ActionColumn'],
          ['class' =&gt; 'yii\grid\CheckboxColumn'],
          ['class' =&gt; 'yii\grid\SerialColumn'],
          ]
  ]); ?&gt;
  </code></pre>
  
  <p>it says </p>
  
  <blockquote>
    <p>Class 'kartik\grid\GridView' not found</p>
  </blockquote>
  
  <p>i use basic version of yii 2 in php storm !
  what should i do for fix this problem ?</p>