SCHEMA-793. Implement AsyncKijiResult.

Implemented AsyncKijiResult, AsyncPagedKijiResult, AsyncMaterializedKijiResult,
AsyncKijiResultScanner, AsyncDataRequestAdapter, and associated tests.

issue: https://jira.kiji.org/browse/SCHEMA-793
I can't register it with the Closer because `org.hbase.async.Scanner` (for some reason) doesn't implement `Closeable`. Should I just add a check for null?