Add showLoadingIndicator option

If you set showLoadingIndicator to false, then created div will not appears on page.

I'm pretty sure that showing that indicator's either text and spinner should be optional.
So my commit contains solution with just hiding indicator's element because it's allow us to not have many if/else statements where we trying access `loading` (e.g. `loading.remove();`) and doesn't affect much code.

If they don't want to see the loader, then I would rather not even add it to the DOM.  Your solution is still adding it to the DOM, but it is hidden which is just wasting cycles IMO.  Can you work on this so that it also doesn't ever add it to the DOM?