`Relation#create_get` get family options, and `families: :relation`.

`families: :relation` includes all families in the relation schema.
Scans get this new option as well.
`ExecutionContext#relation` considers all families when passed an op.

This way, if you get a relation back at all, you can be sure all
families (say, in a passed put) are within.
Merge pull request #104 from seomoz/phs/relation-get-and-scan-can-read-whole-relations

Phs/relation get and scan can read whole relations