title: DT datatable row is not highlighted when using custom callback in a shiny app
body: <p>I am following <a href="https://stackoverflow.com/questions/29794738/shiny-getting-info-from-the-selected-row-in-a-dt-data-table">this example</a> of how to get elements from a row that is clicked on. This works fine except it does not highlight the selected row. Here is the code:</p>
  
  <pre><code>library(DT)
  library(shiny)
  
  runApp(shinyApp(
    ui = fluidPage(DT::dataTableOutput('tab'), verbatimTextOutput('row')),
    server = function(input, output) {
      output$tab = DT::renderDataTable({
        datatable(iris, selection = 'single',
                  callback = JS("table.on('click.dt', 'tr',
                                  function() {
                                    $(this).toggleClass('selected');
                                    Shiny.onInputChange('row', table.rows('.selected').data().toArray());
                                  });")
        )
      })
      output$row = renderText({input$row})
    }
  ))
  </code></pre>