jointly with Tathagata Das and Haoyuan Li. This commit imports the changes
and ports them to Mesos 0.9, but does not yet pass unit tests due to
various classes not supporting a graceful stop() yet.
- Replaced modified Kryo version with the standard one augmented with
the kryo-serializers package, which includes support for classes with
no-arg constructors (that was why we had a modified Kryo before)
- The kryo-serializers version also fixes issue #72.
- Added a bunch of tests.
- Serialize maps and a few other common types properly by default.
