Add Hadoop platform test to enable unit testing for Hadoop semantics

Pig has it, Cascading has it, now Scalding can have it too. Currently, all of the unit testing uses either Cascading's local mode, which uses Hadoop's local mode. There is a certain class of bugs which, as a result of this, cannot be caught (this is actually why if you run these tests they don't pass...there is a bug in Cascading! expect an update soon).

There are definitely areas for improvement in the API and whatnot but I wanted to get this out there so I could get comments