Bundle updates in spec/app and fixes for running tests with Ruby 2.1.1
Make test more descriptive
Rename spec
Remove unused method
Add some specs
Use datasets in place of static lists as much as possible

Also, rely on the Sequel adapter being capable of providing the first id
inserted in bulk inserts and on the ids being consecutive.

This is generally the case in MySQL with InnoDB tables, when the option
innodb_autoinc_lock_mode is left at its default value (1 --
"consecutive") or changed to 0 ("traditional").

The other possible value for the option is 2 (interleaved), which makes
the ids possibly interleave under concurrency, and render our
assumptions false.

Thus, AccessControl now requires a database configured to always
generate ids in consecutive order for a given bulk insert and a Sequel
adapter for the database capable to retrieve the id of the first row
inserted.
Be resilient with circular parent-child relationships
Use insert instead of import

This actually promises an integer as the id of the inserted row, as in
the docs.  Note that this is adapter dependent, and thus AccessControl
requires a compatible database (also refer to
bc82e29f8432ce30cc31d5010334897f77a71cd8).
Improve performance