Inline expansion for Dropbox "shared" images

Adds a handler for dropbox "shared" image urls.

Requires no requests other than the fetching of the actual image.

Images shared from the "Public" folders of those who still have them will be unaffected as those are hosted on a different domain.
Could you explain what you mean? I was planning to use splice at first, but I felt this solution would be more readable. Is there something I've missed?