Rich hdfs

* Adds function to lift hdfs to execution
* Removes scalding stuff from maestro package.

I'm not sure about the second change. Right now I don't think the scalding imports we expose are comprehensive enough but do we really want to expose a lot of scalding or let the user pull in themselves what they need. In that case we don't want to force our users to have to deal with shadowing though.
:+1: