Gridster's `add_widget` ultimately passes on the first parameter to
jQuery, and jQuery accepts either a string, a DOM element, or a
jQuery object.
`add_widget`'s first parameter should reflect what jQuer supports.
The current situation force the user to have a not necessary creation of
an HtmlElement object. In fact, you do not need. JQuery Gridster has a
plugin that take a single parameter which is the option. This is why
that Pull Request fix this issue but also the issue that when debugging
the unit test you can see that the injected options were the HtmlElement
instead of the real options.
