link needs to be relative to the root, as this is gets rendered when the browser's location is /index.html; the browser's location is not /modals/piu-modal.html
Matt Gasior needs to be able to target each popup div differently in his CSS, so we need to add a distinguishing class to the dynamically added div
doh, use a selector that will work in production -- staffweb.cru.org doesn't have a div#piu-modal-container
Merge pull request #8 from mattdrees/master

ability to add distinguishing CSS classes to modal divs