Add sumOption support for Tuples
update to 0.13 so it can compile on travis
Merge branch 'develop' into tuple-sumOption

Conflicts:
	project/Build.scala
Merge pull request #242 from twitter/tuple-sumOption

Add sumOption support for Tuples
Update CHANGES, build
Merge branch 'release/0.3.1' into develop
Fixes #229: applied math.abs after the modulo in the nextHash, added scalacheck
that the new indices are non negative and a test for the problematic case
tabs replaced
moved the abs logic into the splitLong function, made BFHashIndices test generic
Merge pull request #243 from natapov/develop

Make BFHash take on non negative values only, issue #229
Make the map monoid more performant for mutable maps
fix up typo
adds append method to MonoidAggregator and RingAggregator
renamed fold to append
renamed fold to append, switched to ring.one from ring.zero
moved append and appendAll to base trait
Merge pull request #246 from MansurAshraf/develop

adds append method to MonoidAggregator and RingAggregator
avoid copy from mutable
Revert "avoid copy from mutable"

This reverts commit ed5a9425bc19c06cbd27041d52a2e30f17025468.
make an immtable backed map