ActiveResource validation tests did not test ActiveModel validations. Adjust the test to be done the Rails3 way.
Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>

Added validations to ActiveResource. Added a smoke test to see if we can add a validation and use it, and add a validates callback and use it.
Signed-off-by: NJoshua Peek <josh@joshpeek.com>