Improve performance of large option lists

I've noticed large option lists in selects cause the browser to timeout when rendering selectize.
Detaching the input, then detaching the children from it,
then re-attaching the input dramatically improves performance.

[skip-ci]

src/selectize.js

@@ -225,8 +225,13 @@ $.extend(Selectize.prototype, {
 
 		// store original children and tab index so that they can be
 		// restored when the destroy() method is called.
+		// Detach children outside of DOM to prevent slowdown on large selects
+		var inputPlaceholder = $('<div></div>');
+		$input.replaceWith(inputPlaceholder);
+		var inputChildren = $input.children().detach();
+		inputPlaceholder.replaceWith($input);
 		this.revertSettings = {
-			$children : $input.children().detach(),
+			$children : inputChildren,
 			tabindex  : $input.attr('tabindex')
 		};