Fixed Inboxen/website#61

Outstanding issues:
* massive amounts of task requests are left in the queue, we kinda need them to find out when a task has finished, but need to find a way to throw them away after
* tasks should be split along lines of blocking code. e.g. when we spin off a group task to grab mails a separate task for tarballing should be chain()'d to it rather than the have a running task wait
* give nicer names to the resulting tarball
We can now raise the limit on delete tasks