Preliminary SLURM and Travis-CI support

Hey Brad,

I managed to run the pipeline via SLURM with the changes from @vallens feature branch/pull request we put together in the hackathon:

https://github.com/roryk/ipython-cluster-helper/pull/6

```
bcbio_nextgen.py ~/config/bcbio_system.yaml config/project1.yaml -t ipython -n 12 -s slurm -q node -r "account=a2010002;timelimit=04:00:00"
```

The Travis support needs more work, though:

https://travis-ci.org/brainstorm/bcbio-nextgen/builds/9392051