add 3rd-party jars via python

[bjuergens]

currently you need to call this with something like this:

pyspark --jars $HOME/dev/dirhash/target/sparkhacks-0.0.1-SNAPSHOT.jar dirhash.py /smartdata/ugfam/dev/test_data/raw/

But it would be better with something like this:

pyspark dirhash.py /smartdata/ugfam/dev/test_data/raw/

You can add the jars via python, as suggested here.