Talk about why we return the jQuery selector instead of Kendo UI widget, from jQuery methods

This is one of the things that confused me the most when I first started working with Kendo UI's controls - I didn't understand how to get access to the control instances, and didn't understand why I needed to call the jQuery `data` method to get it. It took me a while to realize that we are just following the jQuery convention of always returning the original selector from the method, instead of our widget instance.

I've updated the Getting Started docs for widgets to mention this. Hopefully this (or some better version of what I wrote) will help others make the connection faster than I did. :)