A Cascading scheme for combining intermediate sequence files

A cascading scheme for SequenceFile that uses EB's `DelegateCombineFileInputFormat`. 
This will allow us to turn on split combination for all intermediate jobs in a cascading pipeline (currently we can only turn it on for initial LZO sources).
Oh, you are right. 

I originally tried to do a generic approach of pulling the intermediate input format from cascading, do this wrapping, and put the new one back, and this was left over from that. I'll change it.