Got `git annex export` working to external special remotes. Each external
special remote will need some modifications to allow exporting. Exporting
to some things doesn't make sense, but often there's a way to browse a tree
of files stored on the special remote and so export is worth supporting.
Now would be a good time to contact the author of your favorite special
remote about supporting export..

Also had time to get `git annex export` working to S3. The tip 
[[tips/publishing_your_files_to_the_public]] had a clumsy method for
publishing files via S3 before, and is now quite simple!

Today's work was supported by the NSF-funded DataLad project.
