Add lift and liftOption methods to Aggregators

This is useful when you have a common call site that expects to use
the standard Aggregator API (prepare, present) but in some cases you
wish to aggregate values that come as Option or Collection types.
Use OptionMonoid
Rename to lift and sumBefore
Update README.md
Make CMSHasher trait serializable so it works with e.g. Storm
Make HeavyHittersLogic serializable
Make HeavyHitters serializable
Make HeavyHitter serializable
Make CMSHash serializable
Merge pull request #382 from miguno/GH-381

GH-381: Fix serialization errors when using new CMS implementation in Storm
Change function of lift

Now returns MonoidAggregator[A, Option[B], Option[C]].
Also update and simplify some tests, and style fixes.
Fix snoble's name
Merge pull request #384 from mlmanapat/mlm-fix-snobles-name

Fix snoble's name
MonoidAggregator.sumBefore returns MonoidAggregator
Merge pull request #380 from danielhfrank/lift-aggregators

Lift methods for Aggregator and MonoidAggregator
Add code coverage via coveralls

https://coveralls.io/r/twitter/algebird

Signed-off-by: Chris Aniszczyk <zx@twitter.com>