kiji-express: EXP-335. Convert the kiji-express-example project into a module.

issue: https://jira.kiji.org/browse/EXP-335
review: https://review.kiji.org/r/1466
commit: https://github.com/kijiproject/kiji-express/commit/57d11957657e641c4ac47ddb2bfe9cb38c76cbfa