This is a branch that will be kept updated to work with seance
even if the original at github:xdamman/mediumexporter#master
takes time to pull in changes
Some publications, including Snipette, use an image in place of
section breaks. These images should be filtered out for Ghost and
replaced with a linebreak ('---') because the image will be added
later via CSS or something. Also, this means we don't have to
unnecessarily re-upload the pics multiple times and for mulitple
posts
