resend different messages when one fails

[infinity0]

Pond is repeatedly trying to send to a remote server which is offline, meaning that messages further down in the queue aren't being sent.

A good fix would be to try a different message the next time. Another possible fix (which I think should still be secure, but maybe not) would be to have separate queues for each server, so that one server going down doesn't affect others.

Related are #134 and #81. The former would give me a way to workaround the bug; currently my Pond client is effectively disabled for sending messages. >:[

[burdges]

Just submitted pull request #156 to fix this. :)

It'll have the side effect of scrambling your outbox order if your machine is offline, like when you unsleep your laptop, so maybe @agl would prefer that connTrouble() check to see if Tor is working at all.

[burdges]

Now fixed in master so this issue should probably be closed. I still worry that messages should not be reordered if tor or the network is down outright, but hey.