worker: add heartbeat
worker: remove host only worker pruning
worker: shut down gracefully on SIGTERM in borg
Fix failure handling for resque-jobs-per-fork when child is KILLed.

When the child job process is killed with the KILL signal, needs to handle
the failure hooks for the child.  Normally resque only processes a single
job in the forked child, so it uses the job instance that is already in
memory in the parent process. However, this with resque-jobs-per-fork, this
is just the first job processed by the child, since it pops more jobs off
the queue.  Instead we need to get the job payload from redis.
Kill jobs from Resque web interface
Add SIGHUP bullshit because golang (and therefore docker) can't forward SIGCONT