fake-hbase: POM-40. Require JDK 7 to compile Kiji projects

issue: https://jira.kiji.org/browse/POM-40
review: https://review.kiji.org/r/2003
commit: https://github.com/kijiproject/fake-hbase/commit/e8987afb23b28b95b869bfc14d6ac5a6bfcff061