Use a spinner to indicate upload is in progress. (#358)
Add a ajax view to handle image rejection (#358).
Add links to delete uploaded sighting photos. (#358)
Make some minor fixes to the rejection handler. (#358)
Tie photo removal link to the ajax handler. (#358)

When the ajax handler successfully rejects an image, delete it from the
DOM and remove the hidden input that will associate it with this
Sighting.  Use a fadeOut transition on removal just so it's a bit more
obvious to the user what's going on.