Move relationship tests around

diff --git a/t/relationship_after_update.t b/t/relationship/after_update.t
similarity index 100%
rename from t/relationship_after_update.t
rename to t/relationship/after_update.t

diff --git a/t/66relationship.t b/t/relationship/core.t
similarity index 100%
rename from t/66relationship.t
rename to t/relationship/core.t

diff --git a/t/relationship_doesnt_exist.t b/t/relationship/doesnt_exist.t
similarity index 100%
rename from t/relationship_doesnt_exist.t
rename to t/relationship/doesnt_exist.t