Fixes #243 Tuples should no longer be squashed in the event store

I got ya, I was just starting to look through the accept and findTop methods and now see what you mean on the MetadataExpirationFilter.  I will comment below, but it looks like the only method actually used by this base class is the shouldExpireMethod.  Maybe the MetadataExpirationFilter shouldn't actually extend this class and you put the shouldExpireMethod into a utility method somewhere if you want to reuse it.