Update foundation.interchange.js to work with background-image

When a tag(not an image tag) has a data-interchange attribute containing an image path it will set a background-image on element instead of trying to replace the innerHtml.
Fix bug Issue #3630

https://github.com/zurb/foundation/issues/3630
Update foundation.interchange.js
Fix to prevent background-image to change on every resize if not necessary
Adding documentation on interchange with background-image.
Merge support for interchange with images.