portion of thread
_ have "notes" (treated as emails to oneself, never sent) as
first-class objects.
+_ make use of the username in URIs, and move account passwords to
+ a different file from sources.yaml. heck, allow encryption of that
+ file.
for 0.4
-------
+_ bugfix in drafts: the entire thread is currently discarded, rather
+ than just the one message. (need to distinguish per-message and
+ per-thread deletion in the update messages.)
_ bugfix in completion: capitalization for contact names
_ imap: cache headers
_ imap: share connection to the same server.