Phs/refactor crud helper

Drop the crud helper in favor of using the relation client.

`fixture` takes a relation name instead of a table name, and the yielded block should return an array.  Each element should be of the form:

`[row_key, qualifier_name, qualifier, value, timestamp]`

These are each translated to a `Put` and written.

`expect_table` has become `expect_relation`, the expected rows have been pushed down to a block where they should resemble the rows received from `Relation#scan` after `flatten(1)`.

`expect_relation` also now takes qualifier name-value pairs, to select just those columns that are actually in the desired relation.

The content of the blocks in `fixture` and `expect_relation` have identical structure, and should be interchangeable.