add help instructions

Issue Summary

first I would like to thank you for this module, I have found it very useful on my site.

I don't believe most people are going to know about CC and would like to add a little bit if info below the box where you select which one you would like to use. In this text box I plan on explaining just a little bit, but also offering a link to either the onsite handbook or to the actual Creative Commons website where they can learn more.

thanks.