WIP: LSF batch submission Task

LSF is one of a family of batch submission systems in use on academic computer clusters. I thought Luigi is a great fit for my workflow, so I built an LSF Task for Luigi. 

From the small experience I've had using other submission systems, it won't be too difficult to adopt it to other batch submission systems (SGE, SLURM, etc)

I have no idea if this is too niche for the Luigi project, and I don't know what the standard are for contribution (in terms of tests, etc, for which you'd likely need an LSF cluster), but I thought I'd get the ball rolling.