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).
Ah, right. The problem is that `SequenceFileInputFormat` does not implement `MapredInputFormatCompatible` which the mapreduce -> mapred wrapper needs.