[ADAM-237] Migrate to Chill serialization libraries.

Fixes #237 by migrating to Chill's avro serializers. Also bumps the Scala version to 2.10.4, which is used by Spark 1.1.0 and Chill 0.5.0. Ironically enough, it seems that our original serializers were actually the inspiration for adding Avro to Chill! See https://github.com/twitter/chill/issues/171 ;).