Expose the item/group element in option.template and option.groupTemplate

[yotamberk]

This is important for rendering components to the element of the item for libraries like React.
When we want to mount a react component to the template, we have to have the item/group element itself so we can do something like ReactDOM.render(<your template>,element).

You can now use the timeline options templates with react components:

options = {
   template: function (item, element) {
        return ReactDOM.render(<b>{item.content}</b>, element);
   },
   groupTemplate: function (group, element) {
       return ReactDOM.render(<b>{group.content}</b>, element);
   }
}

[mojoaxel]

Looks good.
I specially like the React integrating! Nice! ;-)