Fixes #545

[janmichaelyu]

Callback test function example:

function callbackTest(facet, x, y) {
  console.log('facet', facet)
  console.log('x', x)
  console.log('y', y)
}

angular.extend(ctrl, {
  eyeColor: chartsService.top10Chart('Eye Color', 'pie', 'eyeColor', 'Eye Color', 50, callbackTest),
  gender: chartsService.top10Chart('Gender', 'bar', 'gender', 'Gender', 50, callbackTest),
  combined: chartsService.top10Chartv2('Eye Color vs Gender', 'column', 'eyeColor', 'Eye Color',
              'gender', 'Gender', callbackTest)
});