Vliu explorev2 bugs (#1701)

* Fixed table_name does not exist in druid

* Make Chart container scrollable for large chart

* Fixed bug of action buttons not clickable in heatmap

* Solve codeclimate issue

* Limit overflow to x

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

@@ -204,6 +204,7 @@ class ChartContainer extends React.Component {
               id={this.props.containerId}
               ref={(ref) => { this.chartContainerRef = ref; }}
               className={this.props.viz_type}
+              style={{ 'overflow-x': 'scroll' }}
             />)
           }
         </Panel>