Fixed css class not being used by slice container (#1359)

* Fixed css class not being used by slice container

* Delete require css line since it's not needed when className is specified

caravel/assets/javascripts/explorev2/components/ChartContainer.jsx

@@ -73,6 +73,7 @@ class ChartContainer extends React.Component {
           <div
             id={this.props.sliceContainerId}
             ref={(ref) => { this.chartContainerRef = ref; }}
+            className={this.props.vizType}
           />
         </Panel>
       </div>