Added HTCondor support

I've added a module to support Linux HTCondor clusters assuming:

1. The Julia executable is installed in the same location for all.
2.  Nodes don't block ports within the cluster.

It would probably be better to use a systematic scan to find an open port to use on the head node, but this does work for now.  I started off with the same shared filesystem method used in the SGE example, but it turned out to be painfully slow on our local cluster.