kiji-schema: SCHEMA-888. Use version 2.0.4 of DataStax Java driver

issue: https://jira.kiji.org/browse/SCHEMA-888
review: https://review.kiji.org/r/2079
commit: https://github.com/kijiproject/kiji-schema/commit/0840c6cbc3de192947a82806b8d61813d22d0c7b