Casssandra 1.2 support

This doesn't fully handle RangeTombstone.  In fact it just ignores the problem and I think we will sort it out when we handle columns individually.  The problem is that RangeTombstones give a min/max column that they apply to, which needs to be handled in the correctly sorted order of columns after they are compacted.   One way to handle that is to send the list of RangeTombstones to the reducer and just compare every column against them as we process the row.