When called, the callback passed to HTTPGetter.get() is now explicitly
passed the URL and the http.client.HTTPResponse instance.
Remove the HTTPGetCallback.result attribute (not needed anymore, leaves
more freedom when implementating HTTPGetCallback subclasses...).
If the response to the HTTP request isn't 200 (success), then don't save
the response, and don't call the callback.
Additionally, only retry in the case of HTTPException. This allows using
Ctrl-C to work correctly (and easily).
- add option --quick
check sha1sum of .dirindex files and skip directory if hash matches
- add option --remove-orphan
remove orphan files (files exist locally but not on server)
- be less verbose
- write .dirindex files locally
