Beginning of multi-thread.

Eliminate the central queue object, and allow the socket threads to
actually perform the work to generate their own responses.

Don't get excited, almost everything is wrapped up in a massive global
lock.
Revamp reddit plugin, quicker, better
First stab at proper coarse multithreading

This yields some performance benefits, like the feed indexing and
plugins being done from in the fetch thread, which in turns means that
the daemon becomes responsive much faster and can process requests
faster on average.
Minor fixes - work_done hook called from fetch thread

This lets the thread send out tag change notifications.
Fix self.items == None

Signed-off-by: Jack Miller <jack@codezen.org>
Fix tag configs being lost

Since instantiating Feed() objects no longer actually performs the
index(), we haven't populated the tags by the time we weeded out the
tags that have no items.

In retrospect trimming the tag configs was a bad idea anyway, the lazy
change just made it worse.