Rationale: some services thought that images linked from /posts/upload
are hotlinked. This is because they were receiving referrer set to a
host that is unknown for them. By using proxying, referrer is blank,
which increases thumbnail coverage at the expense of increased
server-side traffic.
Since the purpose that StatusHelper was mainly created for no longer
holds, it was simplified to Messenger. It is now is used to transport
simple messages to views and still transports info whether the message
is about success or failure.
