Chance pivot reduction size calculation.

The larger justification for this is that we are going from the
far more efficient thrift representation into strings. So there
is an explosion of size. With this set to 1.gb it resulted in
too much being sent to each reducer. The magic number isn't
great, but at least this one should work a bit better.
Merge pull request #314 from ambiata/topic/pivot-size

Chance pivot reduction size calculation.
Switch copyright to Ambiata.
Merge pull request #318 from ambiata/topic/licence

Switch copyright to Ambiata.
Add date as primitive type to Ivory

Ingest thrift for dates is a string, not a packed int
Merge pull request #315 from ambiata/topic/date-primitive

Add date as primitive type to Ivory
WIP: Reducageddon
Moar reducers and date stuff
Proportion by time
Tombstone handling (maybe)
Fixes for sum_by and a few other changes
Fixed dictionary filter validation
Finishing touches. Still missing big cli test
Add key type param to KeyValue and support ints in count_by
Fixed NumFlips and count days test
Extra changes required for Dates