kiji-express: EXP-414. Split out KijiInput related source tests to KijiInputSuite.

issue: https://jira.kiji.org/browse/EXP-414
review: https://review.kiji.org/r/1632
commit: https://github.com/kijiproject/kiji-express/commit/d9f3087f5516dc8d30d138bdc5a7294fae5d894c