Tool to parallelize "mega" python ntuple analysis jobs using condor

cc @mverzett @mcepeda

Does what it says on the tin.   Works as drop-in replacement for the local ``mega`` command, ``s/mega/mega-farmout/g``.  The script submits the job, automatically merges the output using a Condor DAG, waits for everything to complete,  and then copies it back to the local area.

```shell
mega-farmout WHAnalyzeEMT.py inputfiles.txt output.root --tree "emt/final/Ntuple" --files-per-job 4 --files-per-merge 10 --verbose
```

There are a couple of important features:

* ``--files-per-job`` determines the number of files processed per condor job
* ``--files-per-merge`` determines number of files merged per merge job.  The merge will automatically proceed in layers until only one file is left.
* The files in inputfiles.txt have to be on HDFS