Okay, I have an update: your plugin wasn't working because I had the Pinterest button enabled in the social share bar plugin I had. When I disabled the Pinterest button in my social share bar plugin (TF Social Share), your plugin worked perfectly!
I prefer your plugin since it shows up with every image... but I would def. prefer if clicking the "Pin It" button didn't navigate you away from the page. When I have both plug-ins enabled and your pin it button shows up next to the image, it does the typical Pinterest popup, but when I only have your plug-in enabled and the "Pin It" button appears overlayed on the image, it navigates you to a new page.
Thanks again for staying in touch.