Revert "Simpler fix for updating hidden sliders (#1010)"

This reverts commit 4e1caee7da.
See https://github.com/rstudio/shiny/issues/1010#issuecomment-169971201

srcjs/input_binding_slider.js

@@ -1,3 +1,11 @@
+// Necessary to get hidden sliders to send their updated values
+function forceIonSliderUpdate(slider) {
+  if (slider.$cache && slider.$cache.input)
+    slider.$cache.input.trigger('change');
+  else
+    console.log("Couldn't force ion slider to update");
+}
+
 var sliderInputBinding = {};
 $.extend(sliderInputBinding, textInputBinding, {
   find: function(scope) {
@@ -52,9 +60,10 @@ $.extend(sliderInputBinding, textInputBinding, {
     } else {
       slider.update({ from: value });
     }
+    forceIonSliderUpdate(slider);
   },
   subscribe: function(el, callback) {
-    $(el).on('change.sliderInputBinding update.sliderInputBinding', function(event) {
+    $(el).on('change.sliderInputBinding', function(event) {
       callback(!$(el).data('updating') && !$(el).data('animating'));
     });
   },
@@ -84,6 +93,7 @@ $.extend(sliderInputBinding, textInputBinding, {
     $el.data('updating', true);
     try {
       slider.update(msg);
+      forceIonSliderUpdate(slider);
     } finally {
       $el.data('updating', false);
     }
@@ -195,6 +205,7 @@ $(document).on('click', '.slider-animate-button', function(evt) {
           val.to = val.from + (slider.result.to - slider.result.from);
 
         slider.update(val);
+        forceIonSliderUpdate(slider);
       };
       var sliderStep = function() {
         // Don't overshoot the end
@@ -205,6 +216,7 @@ $(document).on('click', '.slider-animate-button', function(evt) {
           val.to = Math.min(slider.result.max, slider.result.to + slider.options.step);
 
         slider.update(val);
+        forceIonSliderUpdate(slider);
       };
 
       // If we're currently at the end, restart