Update README.md

Claudéric Demers · web-flow · commit 1260f22476c7 · 2017-01-29T20:53:44.000-05:00
diff --git a/README.md b/README.md
@@ -138,7 +138,7 @@ In root folder:
 Need to sort items in a grid? We've got you covered! Just set the `axis` prop to `xy`. Grid support is currently limited to a setup where all the cells in the grid have the same width and height, though we're working hard to get variable width support in the near future.
 
 ### Item disappearing when sorting / CSS issues
-Upon sorting, `react-sortable-hoc` creates a clone of the element you are sorting (the _sortable-helper_) and appends it to the end of the `<body>` tag. The original element will still be in-place to preserve its position in the DOM until the end of the drag (with inline-styling to make it invisible). If the _sortable-helper_ gets messed up from a CSS standpoint, consider that maybe your selectors to the draggable item are dependent on a parent element which isn't present anymore (again, since the _sortable-helper_ is at the end of the `<body>`).
+Upon sorting, `react-sortable-hoc` creates a clone of the element you are sorting (the _sortable-helper_) and appends it to the end of the `<body>` tag. The original element will still be in-place to preserve its position in the DOM until the end of the drag (with inline-styling to make it invisible). If the _sortable-helper_ gets messed up from a CSS standpoint, consider that maybe your selectors to the draggable item are dependent on a parent element which isn't present anymore (again, since the _sortable-helper_ is at the end of the `<body>`). This can also be a `z-index` issue, for example, when using `react-sortable-hoc` within a Bootstrap modal, you'll need to increase the `z-index` of the SortableHelper so it is displayed on top of the modal (see [#87](https://github.com/clauderic/react-sortable-hoc/issues/87) for more details).
 
 ### Click events being swallowed
 By default, `react-sortable-hoc` is triggered immediately on `mousedown`. If you'd like to prevent this behaviour, there are a number of strategies readily available. You can use the `distance` prop to set a minimum distance (in pixels) to be dragged before sorting is enabled. You can also use the `pressDelay` prop to add a delay before sorting is enabled. Alternatively, you can also use the [SortableHandle](https://github.com/clauderic/react-sortable-hoc/blob/master/src/SortableHandle/index.js) HOC.
